US1612493A - Internal-combustion engine - Google Patents

Description

Dec. Z8', 1926.

H. H. CUTLER INTERNAL COMBUS TI ON ENGXNE Filed March 22', 1924 Z5 Sheets-Sheet l Dec. 2s, 1926.

H. H. cUTLER- INTERNAL COMBUSTION ENGINE Filed March '22, 1924 s sheets-sheet g amsa H. H. CUTLER INTERNAL COMBUSTION ENGINE Dec. 2 8, 1926.

Patented Dec. 2s, 192e.

1,612,493 PATE-NT OFFICE.

HENRY H. CUTLER, or BnooxLINE, MASSACHUSETTS.

INTERNAL-@111131115121611 ENGINE.

Application led March 22, 1924. Serial No. 701,051..

My invention relates to internal combustionengines and more especially to such engines of the variable clearance type in which means are provided for varying theclearance space in unison with the movement of the power piston whereby the volume of such 4clearance space is made to4v vary injsucli close relation to the load upon the engine that the degree of compression maybe maintained practically constant at all loads. j

A further object of my invention is to utilize the same mechanism for mechanically scavenging the cylinder after every explosion, and a still `fur-thcrobject of my invention is to provide a very large amount of resilient recoil at the time of'each explosionof the working mixturein the/.en-l gine cylinder whereby vthe strain upon the.

crank shaft and the reciprocating partsis reduced to from one-.half to one-third of norv mal, thus makingitpracticable to employ Show embodiments of my Vinyention-T Figure 1 is a central vertical section of engines without producing knocking.'

4a compressionpressuretwice as high aspossible lin the usual 'fornik of combustion The-presentinvention is a development ofv that disclosed in'my application Serial No. 445,690, filed February 17, 1921, of

which this' application is a continuation.

the-air' cannot escape during the operation of thef'engine, so that the pressure of` this confined air may be kept approximately constant, and utilized to control the resulting and corresponding compression in the engine This feature I obtain by .noveli .means as .well as' the' usev of modeign and cylinders.

recently developed methods of manufacturlng. A f. I l V .A i.

In the accompanying drawing.S which .one of the cylinders of 'an internal combustion engine, embodying-myv invention, and

of the power piston of the Fig. 2 is a similar section "showing .the-` relative position of the same moving parts on completion of the compression' stroke ;4 Fig. 3 is another similar section showing the position of the same moving parts' at the beginning of the power stroke, or just after the working mixture has been fired;v

Fig. 7

The principal feature of my invention is' theA provision'fof an air reservoir from which Fig. 4 is a top plan viewof -a four-cylinder engine embodying my invention, and showing certain electrical and pneumatic connections and appliances;`

. Fig. 5 is ay development of the .commutator; l

Fig..6 is a horizontal section takenon line C.-D of Fig. 2iand showing a top view of the electro-magnet;

Fig. 7 is ato plan view (partly in section) through-line -B of Fig. 1 of a four cylinder engine embodying-my invention, and showing a method of controlling the electromagnjts ,differing from that shown in Figs. tand-35;.' i.

Fig., 8, is an elevation,- partly insection, on an enlarged scale, of the pressure-actuated electriccircuit breaker illustrated in '.In the drawings which are 'to' be taken as illustrativemerely, and not as restrictive, I show yin.place.o;t the usual demountable head, yasingl'emuiiit head consisting of the casting. 17, secured. by bolts 17 .(Fig. 4f), to

the top `of the cylinder block v414- in .the .usual manner. In the casting 17, cy1inders 18,19,

2 0 and 21 are `formed-and cgnstitute extensions` (of. preferably smaller diameter) of 'the corresponding..cylinders ofthe-main en. gine block 14. :At the extreme endfof each of the'sewcylinder.extensions is a` fixed head or plug,J 22; each'head being hollow andA connected with the water jacket by passage- . ways 26, 26. It` is essential that these fixed heads' 22 shall make a gas and lwater-tight joint with'the walls ofthe cylinder in which they are placed. This result I obtain hyaccurately grinding, the heads 22 `a few thousandths of an inchularger in diameter than the bore'of the cylinders, then heating the entire cylinder casting ,17 and placing the heads therein cold, so thatwhen the cylinder headpasting 17 cools, the heads 22 are firmly gripped. This process has.. been found in practice .to besuicientnot'only to make a perfect water 'and gas-tight joint, but also to stand the pressure of the exploded gases vunder working conditions.

Arranged for longitudinal movement in each cylinder'is a member 28, the portion or volume of each cylinder between each power 'piston 32 and said movable member 28 forming a compression chamber 75,- and means are .provided for al'itomatically controlling the position of said movable member 28 -so as to vary the volume of -said compression chamber 75 in practically exact accordance withthe variation of the load on the engine,

thus keeping the degree of compression ap proximately the same at all times. The position of said movable member 28 is controlled automatically and resiliently `for the purpose above specified and after each explosion der on the completion of the exhaust stroke ofthe power piston 32, as shown in Fig. 1.l

In Figs. 1 2 and 3 is shown a pressure or. dash-pot piston 39 arranged to work in a cylinder 37 formed'by an extension of the fixed head 22. This extension 37 is preferably a brass casting bored out to precisely the same diameter as the cylinder 18 in the casting 17 and then heated and shrunk onto the plug 22 linst as the casting 17 was also shrunk on. On top of each cylinder 37 is a rectangular flange shaped oil' so that when mounted on one vof the plugs 22 this rectangular flange will abut upon the flange of the adjacent casting 37. These anges are bevelled on all four sides which results in the formation of a V-shaped cavity where the flanges abut against each other. These cavities are vthen filled in with metal melted by the process of electric arc welding. and then the entire surface is planed ofi' smooth.

Each pressure piston 39-is connected with its respective scavenging piston 28 by means of a long rod 40. Said rod is preferably made of low carbon steel, pack hardened, and accurately ground so as to make a free but close t in a carefully reamed hole in the fixed head 22; The lower end of said rod 40 has a head 41 and is held tol the scavenging piston 28 by means of a washer 42 riveted to the bottom of the piston 28 with rivets 43. The head 41 is preferably slightly smaller in diameter than the hole in the piston 28 and the hole in the washer 42 slightly larger than the diameter of the rod so as to allow of a very slight side play of the rod 40 leaving it free to center itself in the hole in A the plug 22, without tendency to bind. Likewise an easy fit is made where the red passes through the pressure piston 39. A nut 44 is then screwed on to the threaded end of the piston rod 40, thus-connecting rigidly together the scavenging piston 28 and its pressure piston 39. A taper pin 44a (Fig. 1) is then driven through the nut 44 and its small end headed over. In the bottom of the rod 40 is shown a cylinder 45 (Fig. 3) arranged to .slide freely in a hole in the rod 40 and pressed up by a spring 46. The end of the cylinder 45 terminates in a rod 47 to which is riveted a conical valve 48 after the rod 40 has been attached to the piston 28. Said valve 48 Seats in the bottoni of the piston 28 so as to form a valve free to open into the engine cylinder' whenever the pressure inthe compression chamber'76 exceeds the pressure in the chamber 75. 'The pressure piston 39 also contains a small valve 50 held down by a spring 51 and seating on the inside of said piston 39, and free to Iopen whenever the pressure in the chamber 77 (formed between the bottom of the pressure piston 39 and the top of the head 22), exceeds to alpredetermined -degree the pressurein the air reservoir or chamber 78 above the pressure piston 39.

Inserted in a circular chamber turned out inthe top of the plug head 22 is a coil of insulated wire 53. The inside terminal of the wire coil53 is soldered to a thin brass tube made to Fit closely over the central pole 54 of thecircular magnet formed in the end of the plug head 22. The outside terminal of the coil 53 passes through a hole in the plug head 22 and then through a threaded hole 55 drilled through the cylinder 37 opposite the hole in the head 22. A threaded bushing 56, preferably of tough insulating material,-is screwed up solid against some asbestos thread packing, thereby forming an airtight packing around the terminal wire of the coil 53. A locknut 57 is also shown in Fig. 1. A brass disc 58 turned slightly larger in diameter than the inside of the chamber which holds the coil 53 and having a hole in the center somewhat smaller in diameter than that of the central magnet pole 54 is then pressed down against a shoulder cut in the poles Vof the electric mag net so as to make an air-tight fit. The depth of this shoulder is such that the top surface T of the brass plate 58 when in position will be about one-hundredth of an inch lower than the surface of the magnet poles so that when the pressure piston 39 makes vmechanical contact -with the poles of the electro-magnet 53, a minute air chamber 77 is formed between,them. A number of slots 60 (Fig. 6) have previously been ground one-hundredth of an inch deep in the outside pole of the magnet 53,

After all the above mentioned parts have been assembled asdescribed, the open tops ofthe various cylinders 37 are covered by a plate casting 61. A depression 62 is cast ,in the said plate so as to form a passageway connecting together all four of the cylinders shown in Fig. 4. The outside edges of the plate 61 are bevelled so that a V-shaped grooveis formed all around the edges, be-

tween the cylinders 37 and the v*plate 61.

rIhis V-shaped cavity thus formedis then filled with, metaly melted .by the process of electric arc welding,l resulting in an absolutely perfect air-tight joint between the plate 61 and the cylinders 37 which it covers. o-r convenience inremoving some of the reciprocating parts, closed threaded ni ples 63 are shown screwed into the top of t e plate 61.. j f The pressure pistons 39 and the wire coils 53 .cannot be removed without first chipping or grinding out thermetal melted into the V- shaped groove` inthe plate 61. v f,

The magnet coilsr53 are shown in Fig. 4 as being energized and tie-energized by means of a small commutator 64 mounted. at the end of the casting 17 and driven by asmall sprocket wheel 65, connected by a chain with another sprocket `wheel 65 mounted on the rojecting end of the engine crank shaft, said) sprocket wheel 65*3L having one-half the number of teeth as the wheel 65. The commutator 64 -contains live sets of rings 66 embeddedein insulating material. The rings 66 make contact with live brushes 67. Four ofl these brushes 67 connect with the outside terminals of the four magnet coils,53 respectively. The fifth brush 67e connects with the ,negative terminal ofthe storage'battery 68 after first passing through a small 4rheostat 69 which. controls thel amount of current supplied by the storage battery 68 to all'of the magnet coils 53. The rheostat 6.9 is supplied with four extra contact buttons 70.' which connect directly as shown, with the four coils/53,*respectively.

The rheostat is alsov provided with a segment'71, which segment is connected with the primary vcoil or coils of the ignition tion, in which position the `circuit is open both to the ignition cdil or coils and all the magnet coils 53, Movingy the lever 72 to the right closes the ignition circuit and also such of the magnet coils 53 as are connected yby means of the brushes 67 and commutator segments 66. Moving the rheostat lever 72 to the left first opens the ignition circuit and then connects all the magnet coils 53 .directly across the battery 68 Without first including` any of the resistance of the rheostat 69. A small flat steel spring 121 shown in Fig. 7 returns the lever 72 to the off position, if the lever is moved tothe left and then. released. t

Fig. 5 shows the development in one plane ,0f the outside circumference of the commutator 64. All of the white segments are electrically dead, so that whenever one of the brushes 67 makes contact with a white.

segment, the circuitis broken. The black segments are all electrically connected with the complete ring segment 67 which connects v with the negative of the storage battery 68 through the resistance lof the rheostat 69. Spark plugs 74 are shown in Figs. 1, 2, 3 and4. l l

The air reservoir 7 8 (F ig. 4) is connected by piping with a Bourdon pressure gauge 81, and 'also-to a taper gas cock 82. small hand-operated air pump 83-is connected to the gas cock 82. The said cock 82 has two' holes drilled from the outside at' right angles to each other and meeting in the center as shown in Fig. 7 soy that by turning the cock 82 in one direction the reservoir 78 may be connected with the outside air, and by turning the cock `in'the other direction the air reservoir 78 may be connected with the air' pump 83. All threaded pipe connections, etc., are `preferably electric welded.

Before assembling the above mentioned parts of my invention, each pressure piston 39 istemporarily fastened to its piston rod ,40p which is then inserted in the hole reamed out in theplug head 22. The piston 39 is then ground against the poles of the magnet 53 so as to make an air-tight valve between the bottom of the piston 39 and the central pole 54 of the electro-,magnet 53. of the electro-magne't are scraped by hand so that the piston 39 will touch only the central pole 54, the surface of which may also be hand scraped together with the contacting surface of the piston 39. v

Having assembled all't-lie above described parts and made allof the electrical' and The high spots on the outside pole f los" pneumatic connections shown and described,

the rheostat lever 72 is moved to the left so as to fully energize all four of the magnet coils 53 and cause all four of the pressure pistons 39 to be held firmly against the central poles 54 of the electro-magnets. The

rheostat lever 72 may then be released 'and thus allowed to return .toits open circuit or off position. Thefelectro-magnets 53 having thusbeen fully magnetized will retain sufficient` residual vmagnetism to'liold the pressure pistgns 39 toy their seats, and thus preservean vair-tight joint between' the air reservoir'78 and the only ossible avenue of escape fonany air in the reservoir 7 8 by leaking bythe outside of the long piston rods40.

vThe taper .cock

t g' 82-may be turned so as to( 'connect the air pump 83 with the air reservoir 78 and `filtered air free from dust i pump into l,the reservoiruntil ithas reachedV a pressure as shown thegauge 81,.ofsay,

figures about one-eighth Athe volume of a thirty by three and one half inch automobile tire.

The perfection of the air-tight reservoir is obtained by iirst abandoning any attempt to confine this air back of a piston equipped with piston rings as with such construction ithas been found impossible to confine the air, second, by eliminating all gaskets, and stuffing boxes subject to mechanical wear, and third, by electric welding each and every joint.

Figs. 7 and 8 show a different method of controlling the circuit of the electro-magnet 53. Fig. 8 is a full size detailed drawing showing a small cylinder 101 containing a small piston 102 normally held down on its seat by a spring 103. The threaded end of the cylinder 101 is preferably screwed into the casting 17 over the valve chamber in a similar manner as the spark plugs 74, so that the piston 102 is at all times exposer to the pressure in the engine cylindery and free to move up as soon as the pressure in the engine cylinder becomes strong enough to'overcome the pressure of the little spring 103. The end of the piston 102 terminates in a rod 104 arranged to slide freely through a hole in the threaded cap 105 which closes the cylinder 101. The threaded end of the rod 104 is screwed into a button 106 of insulating material. This button when moved upwards by the piston 102 and its rod 103, presses against a flat steel spring 107 which is fastened .to a binding-post or block 108 The other end of the flat spring 107 is riveted to a piece of coin silver 109. The silver point 109 makes mechanical and electrical Contact with another piece of coin silver 110 so as to make a scraping contact as distinguished from a button contact, which irst method has been found by long experience to be much more reliable. The silver contact piece 110 is fastened to another binding block 111. The entire electrical mechanism just mentioned is mounted on a block of in'- sulating material 112 which isscrewed to the casting 17 as shown in Figs. 1 and 7. Mounted also on the block 112 is a small lamp receptacle 113 holding a small incandescentlamp 114 designed normally to burn at a pressure of from 12 to 15 volts. One terminal of the lamp 114 is connected to the binding block by means, of the wire 115, and the other terminal of the lamp connects by means of wire 116 to the casting 17. Each binding block 111 is connected with the outside terminal of its respective magnet coil 53, there being one of the above described pressure-actuated electric circuit breakers for each cylinder of the engine. All the binding blocks 108 are connected electrically by the wire 117 which terminates in the end terminal button 118 of the rheostat 69. The hub of the rheostat lever 72 is connected by means of the wire 119 with the negative terminal of the storage battery 68. The rheostat lever 72 is shown in its open circuit or of position. Moving the lever 72 to the right closes the circuit to all the magnet windings 53, including any desired portion of the rheostat lresistance in circuit. Moving the rheostat leverV to theA left makes it contact with the short circuiting button which is connected by a wire 120 with the terminal button 118 of the rheostat 69. A Hat spring 121 pushes back the rheostat lever 72 to the off position if moved to the left and then released.

All the electric switches above described are normally closed so as to keep the magnet coils 53 energized. These switches are opened however with a quick snappy motion as soon as the compression stroke of the engine increases the pressure sufficiently to lift the little piston 102. This opens the circuit to the respective magnet coil 53 and the extra current induced in the magnet coils on the opening of the circuit discharges through the non-inductive resistance of the filament of the little lamp 114, thereby preventing any destructive arcing between the silver points 109 and 110.

On the opening of the exhaust valve of. the engine, the pressure drops in the engine cylinder, the little piston 102 returns to the position shown in Fig. 8, the switch 107 closes, and the magnet'coil 53 becomes energized again.

The operation is as follows On account 0f the very large amount of resilient recoil which occurs at the moment the working mixture is tired, an engine em- 115 of 150 pounds gauge and a mixture unadul- 120 terated with a large percentage of exhaustgases, the 'firing of such a mixture results in an extremely violent explosion which breaks the spark plugs and tends to smash up things generally, unless a liberal amount 12" of resilient recoil is provided. It is like firing a coast defense gun bolted to a solid foundation and unprovided with a large resilient recoil.

With air in the reservoir 78 compressed 130 to 150 or even 100 pounds, itis evident thatA the power piston 32 will have to approach` ver close to the scavenging piston 28V on its lnward compression stroke before suiiicient compression pressure will develop to force the pressure piston 39 Amore than a few hundredths of an inch from its seat. The. scavenging piston 28 will then (theoretically) assume a position similar to that` shown in Fig. 2, but practically the explosion will follow so closely afterwards that the piston 28 will have no time to linger in such a position, but will continue its motion and immediately assume a position similar to that illustrated in Fig. 3.

. It is evident that the pressure piston 39 will be shot up into the air chamber 78 by the violence of the exploded gases until a .position is reached such that the greatly reduced pressure in the explosion chamber 7 5 becomes somewhat less than the pressure of the air in thereservoir 78 plus the pressure.

of the air compressed in they chamber 76.4

If-the chamber 76 was of infinite size, then the resulting pressure of the explosion would at once. fall to that of the pressure in the air reservoir 78. With a moderate size chamber 76 it becomes practical to reduce the pressure of the explosion to from one-third to one-half of normal, depending upon the pressure carried in the air reservoir and .the loa-d upon the engine.

At the instant immediately following the explosion the pressure ofthe air underneath the pressure piston 39 in the chamber 77 is very much less than that of the outside atmosphere, while the pressure of the air in the chamber 76 is very much greater than atmospheric pressure. An invitation is therefore extended for air to leak by the piston rod 40 from the chamber 76 into chamber 77 and thereby tend to increase the amount of air in the reservoir 78; later on.l

, at .the end of the power stroke, there exists air ma-v be supplied as shown in Fig. 3.

a theoretical invitation for air to leak back the other way from the air chamber 77 to the chamber 76.

Theoretically speaking, the first tendency seem tcioe the stronger practically speaking if any leakage by the piston rod does occur it is extremely small anddoes. n ot interfere with the operationof the engine.

In case an air leak should develop, extra small hole 90 may be drilled through the end of the piston rod 40 and then plugged up by thescrew 91. Near the middle ofthe hole 90 is a pin hole 92 drilled through the rod 40 to meet the hole 90. The diameter of the rod 40 is also somewhat reduced by a groove 93 surrounding the pin hole 92.

' Further up on the rod 40 is another pin hole 94V drilled to meet the hole 90. For al short period immediately following the explosion the hole 94 enters into thechamber 77, thereby allowing a minute amount of forced down the scavenging piston 28 together withthe pressure piston 39-until the latter 'As .the ipowerp1ston-32 descends into the touches or almost touches the poles of the electro-magnet 53.` While the power stroke lhas been taking place, air from the reservoir 78 has been leaking in a steadily decreasing amount around and by the pressure piston 39 into the chamber 77 underneath p the piston 39 so that whenthe piston 39 approaches closely to its seat on the poles of the electro-magnet 53, a film of air is interposed between them contained in the now extremely small chamber 77. After the engine' has made a number ofrevolutions, the air which leaks by the piston 39, rapidly accumulates5 and being compressed in the chamber 77, the

piston 39 cannot seat itself upon the poles vof the electro-magnet 53. If this action were allowed to go on indefinitely, the pressure piston 39 would be stopped farther and farther away from its seat and would'finally cease to function.\ The function of the electromagnets' now becomes apparent. Approximating the time of opening of the exhaust valve the electro-magnet 53 rbecomes energized'by means of the revolving com-.

mutator 64 (Fig. 4) or the switch 109 (Fig.

7); the magnet 53 then pulls the piston 39v down against its poles, thereby still further compressing the air in the minute air'ch'amber 77, now reduced to a heightof onehundredth of an inch, as previously described. l

, The process of` accumulating air in the chamber 77 continues as the engine operates,

until finally the pressure of the air confined.

in the minute chamber 77 becomes great y enough to lift the relief valvel 50 and thereby return the excess air to the reservoir 78.

A The electro-magnet 53 acts therefore as,an

air pump returning the air to the reservoir 7 8 as fas/t as it manages to leak by the piston 39. The electro-magnet v53 is then kept magnetized until sometime during the corn-v pression stroke (it being immaterial just when), when its brush runs on to a dead segment of the commutator 64 (Fig. 4), or

by the increase in pressure during the con`1` pression stroke lifting the little piston 102 (Fig. 7) whichever system is used. l

The strength of the spring 51and the the poles of the magnet 53 and force out the surplus leakage of air back through the relief valve 50. While the electro-magnets 53 are shown quite powerful relative to the work they are called upon to perform, this work requires so little power that the current used for energizing the electro-magnets 53 may be greatly reduced by means of the rheostat 69.

' It is an accepted fact that all pistons provided with piston rings as used in internal combustion engine leak. Consequently, the scavenging pistons 28 will also leak so that during the compression stroke a small amount of the working mixture will leak by the rings of the piston 28, as well as a y certain amount of lubricating oil. This working mixture however is not lost, but is returned to the engine cylinder by way of the valve 48, together with any accumulation of lubricating o il during the following intake stroke of the engine.

By means of the taper cock 82 and the hand air pump 83, or the compression tank 100 lled with filtered air under high compression, the operator may run the engine at any degree of compression desired. The engine will operate under low compression without any pressure in the air reservoir 78, or the compression can be gradually increased until the working mixture becomes self-igniting. To operate the engine continuously at some predetermined degree of compression, a relief valve (not shown) may be connected with the air reservoir 78 andl excess air allowed to be supplied by means of the holes 90, 91, 92, 93, 94 and 95, Fig. 3, through the pipe 96, connected with an air filter (not shown). It is furthermore possible to operate the engine with the magnet coils 53 permanently energized, since at the beginning of the compression stroke the piston 39 is subjected to substantially the same air pressure on both sides so that a comparatively small amount of compression will overcome the strength of the magnet 53 and lift the piston 39 a short distance from the magnet 53, in which position the air pressure above 'the piston 39 becomes effec-l the poles of the magnets 53, which magnets retain sufficientresidual magnetism to continue to attract the pistons 39, and hold them to their seats after the current is shut off.l

The air compressed in the then minute air' chamber 77 then gradually works its way through the channels back around the pressure piston 39 until the pressure of the air becomes the same on both sides of the piston 39.

I believe it to be broadly new with me to use an air-tight chamber for controlling the position of a movable member located between the power piston and the closed end of the cylinder whereby to vary the volume of the compression chamber in accordance with the variation of the load on the engine.

Having thus described illustrative embodiments of my invention without however limiting the same thereto, what I claim and desire to secure by Letters Patent is:

l. An internal combustion engine comprising in combination a cylinder, a power piston therein, a hermetically-sealed chamber secured to and forming an extension of said cylinder, a fixed head intermediate the ends of said cylinder, a movable member on one side of said head forming a compression chamber of variable volume. between said power piston and saidy movable member, a second movable member on the other side of said fixed head, and means passingfthrough said head and rigidly connecting said movable members, the said movable members being constructed and arranged to pump gas during the operation ofthe engine into said hermetically-sealed chamber and confine the same without any appreciable loss -either .into -the outside atmosphere, or into said compression chamber of the engine.

2. An internal combustion engine comprising in combination a cylinder, a power piston therein, a hermetically sealed chamberenclosing a gas under pressure, and movable means for varying lthe volume of -the compression -chamber of the engine in Amovable means being constructed and arranged to pump gas into said hermeticallysealed chamber and confine the same without appreciableV loss either into theoutside atmosphere or into said compression cham,-I

ber.

4. An internal 'combustion engine com-v prising inV combination, a cylinder, a power pistonv therein, a movable member 1n 'said cylinder, the portion ofthe cylinder between said piston and said member forming a compression chamber, and means for automatically controlling the position'of said member to vary the volume of said compression chamber in accordance with the variation of the load on the engine and for automatically changing the position of said member rto scavenge the cylinder after every eX- plosion. 'n l 5` An internal combustion engine com-k prising, in combination, a cylinder, a power piston therein, a movable member in said cylinder, the portionof the cylinder be- `tween said piston and said member forming a compression chamber, andvresilient means for automatically controlling the position of said member to vary the volume of said compression chamber in accordance with the variation of the load on the engine and for automatically changing the position of said member to scavenge the cylinder after' every explosion.

6. An internalA combustion engine comprising in combination, a cylinder, a ypower piston therein, a movable member in said cylinder, a hermetically sealed chamber forming an extension of said cylinder andA enclosing a gas under pressure, a valve for preventingthe escape of said gas into said cylinder at any point in the cycle of the engine, and means whereby .the pressure ofv said gas will cause said member automatically to vary the volume of the compression chamber in accordance with the variation, of vthe load on the engine, said means being constructed and arranged to pump gas into said hermetically-sealed chamber and confine the same Without any appreciable loss either into the outside atmosphere, or to'sa'id compression chamber. l

7 An internal` combustion engine comprising in combination, a cylinder, a fixed 'head intermediate the ends of said cylinder, a power piston in said cylinder on one side of said head, a scavenging piston located between said' head Aand said powerl piston, said scavenging piston being constructed andl arranged toform with `said head an airtight chamber, a dash-pot piston onthe other side of said head and means passing through said head and rigidly connecting said scavenging piston and said dash-pot piston.

. 8. An internal combustion engine comprising, in combination, a cylinder, a fixed hollow head intermediate the ends'of said terior of said head with-the water-cooling system of the engine, a power piston in saidv cylinder on one'side of said head, `a"s`ca'veng-A lng piston located between saidfhead and cylinder', 'a passageway' connecting' the 'insaid' power piston, said scavengingpistonbeing constructed rand arranged vrto form, with said head an airtightcham'ber, a` dashpot piston on the other side of said `head and means passing through said head and rigidly connecting said scavenging piston -and said dash-pot piston. 9; An internal combustion engine 'comprising, in'combination, a cylinder, a fixed head intermediate thev ends of' said cylinder, a power pistonin said cylinder on one side of said head, a scavenging piston located between said headand said power piston, said scavenging piston :being constructed and arranged to form with said head an airtight chamber, a dash-poty piston on the other side of saidhead, means passingthrough said head and rigidly connecting said scavenging piston and -said dash-pot piston, and a hermetically sea-ledi cylindrical -chamber secured to and forming an extension of said cylinder, 'said dash-potv piston being reciprocable in and closely fitting said chamber, whereby the inward face of said daslrpot 'piston is subjected to the pressure of the gas confined in said Vchamber to limit the inward movement of'said. scavenging piston during 'piston bef-ng reciprocable in and closely fitt'ng said chamber,whereby the inward face of said dash-pot piston is subjected to the pres-sure of the gas'confined in said chamber i to limit lthe inward movement of said scavenging piston during each-power stroke, and a valve located i-n ysaiddaslrpot piston i and arranged for actuation by the pressure in the chamber between the outward face of said dash-pot piston and said fixed head, thereby to open a passageway through said dash-pot piston.,

11. An internal combustion engine comprising, in combination, a cylinder, a fixed head intermedi-ate the ends of said cylinder, a power piston in said cylinder on one side of said head, ascavenging piston located between said head and said power piston,-

a dash-pot piston on thel other side of said' head, means passing through said head and rigidly connecting said scavenging piston and said dash-pot piston, a hermetically sealed cylindrical chamber secured to and forming an extension of said cylinder, said dash-pot piston being reciprocable in and closely fitting said chamber, whereby the inward face of said dash-pot piston is subjected to the pressure of the gas confined in said chamber to limit the inward movement of said scavenging piston during each power stroke, and means whereby the gaseous leakage around said dash-pot piston is forced back into the inward portion of said chamber without loss of pressure.

12. An internal combustion engine comprising, in combination, a cylinder, a fixed head intermediate the ends of said cylinder, a power piston in said cylinder' on one side of said head, a scavenging piston located between said head and said power piston, a dash-pot piston on the other side of said head, means passing through said head and rigidly connecting said scavenging piston and said dash-pot piston, a hermetically sealed cylindrical chamber secured to and forming an extension of said cylinder, said dash-pot piston being reciprocable in and closely fitting said chamber, whereby the inward face of said dash-pot piston is subjected to the pressure of the gas confined in said chamber to limit the inward movement of said scavenging piston during each power stroke, and a magnetically-actuated pump for forcing back intothe inward portion ol said chamber the gaseous leakage around said dash-pot piston.

13. An internal combustion engine comrising, in combination, a cylinder, a fixed liead intermediate the ends of said cylinder, a power piston in said cylinder on one side of said head, a scavenging piston located between said head and said power piston, a dash-pot piston on the other side of said head, means passing through said head and rigidly connecting said scavenging piston and said dash-pot piston, a hermetically sealed cylindrical chamber secured to and forming an extension ofv said cylinder, said dash-pot piston being reciprocable in and closely fitting said chamber, whereby the inward face of said dash-pot piston is subjected to the pressure of the gas confined in said chamber to limit the inward movement of said lscavenging piston during each power stroke, a magnetically-actuated pump for forc'ng back into the inward portion of said lchamber the gaseous leakage around said dash-pot piston, and means controlling said pump synchronously with said power piston.

14. An internal' combustion engine comprising, inv combination, a cylinder, a fixed head intermediate the ends of said cylinder. a power piston in said cylinder on one side of said hea-d, a scavenging lpiston located between said head and said power piston, a

ing an extension of said cylinder, said clash-- pot piston being reciprocable in and closely fitting said chamber, whereby the inward face of said dashpot piston is subjected to the pressure of the gas confined in said chamber to limit the inward movement of said scavenging piston during each power stroke, a

magnetically-actuated pump for forcing backl into the inward portion of said chamber the gaseous leakage around said dash-pot pis ton, and pneumatic means actuated by the pressure in said cylinder for controlling said pump synchronously with said power piston.

15. An internal combustion engine comprising, in combination, a cylinder, a hermetically sealed cylindrical .chamber secured to and forming an extension of said cylinder, a piston reciprocable in and closely fitting said chamber, a Huid pressure reservoir, a conduit connecting said reservoir with said chamber, and means for forcing back into the inward portion of said chamber gaseous leakage around said piston into the outward portion of said chamber without loss of pressure.

1G. An internal combustion engine comprising, in combination, a cylinder, a fixed head intermediate the ends of said cylinder a power piston in said cylinder on one side of said head, a scavenging piston located between said'head and said power piston, a dash-pot piston on the other side of said head, means passing through4 said head and rigidly connecting said scavenging piston and said dash-pot piston, a hermetically sealed cylindrical chamber secured to and forming an extension of said cylinder, said daslrpot piston being reciprocable in and closely fitting said chamber, whereby the inward face of said dash-pot piston is subv jected to the pressure of the gas confined in said chamber to limit the inward movement of said scavenging piston during each power stroke, and a .magnetically-operated valve for preventing the escape around said means of the gas confined in said chamber.

17 An internal combustion engine comprising, in combination, a cylinder, abermetically sealed cylindrical chamber secured to and forming an extension of said cylinder,

a piston reciprocable in and closely fitting said chamber, a rod for said piston, a seatfor said piston surrounding said rod, and an electromagnet for holding said piston to its seat, thereby to prevent the escape around said rod of the gas confined in said chamber.

18. An internal combustion engine comprising, in combination, a cylinder, a fixed head intermediate the ends of said cylinder,

a power piston in said cylinder on one side of said head, a scavenging piston located between said head and said power piston, a dash-pot piston on the other side of said head, means passing through said head and rigidly connecting said scavenging piston and said dash-pot piston, a source of compressed air, andmeans for conveying compressed air to the inner face, of said dash- HENRY H. (BUTLER,

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