US1728363A - Variable-stroke combustion engine - Google Patents

Description

Sept. 1 7, 1929.

ALL. RIGHTENOUR VARIABLE STROKECOMBUSTION ENGINE Filed May 26 1927 4 Sheets-Sheet l P 1929. A. RIGHTENOUR 1,728,363

VARIA BITE v STROKE COMBUSTI 0N ENGINE Sept. 17, 1929. A. L. RIGHTENOUR 1,723,363

VARIABLE STROKE COMBUSTION ENGINE Filed May 26. 1927 4 Sheets-Sheet 3 POWER STROKE (innu. can cofirnzssnou scnvzuema SUCTION Sept. 17, 1929. A. 1.. RIGHTENOUR VARIABLE STROKE COMBUSTION ENGINE Filed ma z's'. 1927 4 Sheets-Sheet 4 Patented Sept; 17, 1929 UNITED STATES PATIENT OFFICE L. RIGHTENOUR, CLIFTON H. ,FRIZELLE, A. J. sxarr, o. E. MCABTHUR, FRANK I. QUEEN, AND 0. 1). LA Fon'rAINE, ALL OF CHICAGO, ILLINOIS, AS 'rnus'mns VARIABLE-STROKE coMBUs'rroN ENGINE Application filed May 26, i927.- Serial No. 194,455.

This invention relates to a variable stroke combustion engine, and particularly 'to a con,- struction wherein the piston is directly associated with an actuating cam formed to vary 5 the length of its stroke for the successive cycles of engine operation during a complete rotation of a driven shaft. I f

In thistype of engine it is important to provide for the maximum length of piston stroke during the exhaust or scavenging movement and the opposite suction or intake travel which involve a one-half revolution of the cam while the minimum length of the piston stroke occurs during thecompression and firing cycles when the piston is at its usual length of stroke. To effect such operation the piston is yieldingly held in contact with a figure 8 cam on the driven shaft and to secure the most eificient action of the piston dur- 0' ing the successive cyclesof engine operation the movements of the piston are difierently timed so that I obtain a variation in the length of piston stroke and also vary the time of opposite movements comprising such strokes. This may be readily accomplished by I forming the opposite cam heads of different transverse width and also by offsetting. oneof the side contact faces of the cam ata greater distance from'the longitudinal center of the cam than its opposite face. The result is to provide actuating faces at opposite sides of each end of the cam having different arcs of curvature which control the movement of the piston relative to the travel of a' given point ofthecam- I I Under this arrangement, when thepiston is at its inward limit of movement after the when the stroke is completed, while the return movem ent' of this stroke comprises the firing or powercycle and is. more rapid than the compression travel which results in the greatest lev erage atthe beginning of the stroke and a reduction thereof until the piston is nearest the axis of the cam at'the completion of the :tourfcycles of operation.

The result'ofthe side variations of the cam face or different arcs of curvature thereof, is that for a fixed distance of circular travel ofa given point on the camthe piston has imparted thereto a different extent of movement during the successive cycles of operation resultingin a much more efficient action than would beproduced were the side faces of the cam equal in curvature and the heads of thesame transverse diameter.

In an engi assemblage cost of repair.

ne ofthis character it is desirable to avoid extended connections such aspiston rods between the piston and its controlling cam and I' have provided for the direct engagement of the piston with the cam whereby a positive action is secured; the engine parts reduced in number and closely nested to efl'ect a material reduction in weight and cost of construction; and providing a simplicity of 'constructionwhich permits quick and reduces to a minimum the Toward this end of direct contact of the piston with the cam; the skirt of the piston is provided with a roller traversing the actuating faceof thecam during its rotationfand restoring springs are extended from'thepiston skirt to'a point on the i casing below the cam; whichiprovides for a yielding con tact between the piston and cam.

In order to guide the piston in its movementbeyond the cylinder flanges are provided at the open end thereof having curved faces conforming to the curvature'of the cylinder which insures a full downward stroke of thepiston in following the curvature of the cam without liability to" side wobbling movement while the relation of these guides is such that the size and weight of the engine tion of the wmay be reduced by the closely nested relapiston and cam with their associated springs and guide.

In assemb ling an engine of the type before Fig'ureQ,

springswithin said chamber for retainingtlie piston and cam in yielding contact.

The invention has for an object to providea novel and improved construction of variable stroke engine including a cylinder and piston therein, a cooperating shaft having a controlling cam thereon for the piston stroke and formed with heads at different distances from the shaft to' vary the length of stroke andwith" means tovary the timing of the pieton travel during the successive cycles inci dent-to a complete revolution of said'cam during the engine operationi A further. object of the invention is to provide'an improved construction =of controlling cam. having its opposite heads extended at different distances from the axis of. the cam',-said headsbeing of different transverse diameters "and having contact faces of variable arcs to effect a difierent timing motion of the piston during its travel upon opposite faces of eitherhead of the cam.-

Another object of the invention is to provide an improved construction wherein the piston directly engages a controlling cam -an'd1is yieldingly held in contact therewith .soas to'securea direct action of'one member upon theother and a closely" nested assembljageofthe parts.

1 A still further object of the invention is to-provide an improved "construction of engine casing having in its body acam chamber anda cylinder atits upper portion communicating with said chamber together-with in- "leta'nd exhaustjports at the head of said cylinder, a; piston therein, and a cam within the chamber ofthe casing adapted-to directly engage said piston.

Other and further objects and advantages of; the invention willb'e hereinafter set forth and thenovel features thereof defined by the appended claims. r

,In:the accompanying drawings:

Figure 1- is a vertical section with parts in elevation IS a similar view taken'at a right angle toFigurelg Y e i Figure 3 is a diagram illustrating the relative cam and piston movements;

'Figure 4 isa section on the line 44 of 'F1gure'2;"- Y

Figure 6 is a detailsection of the piston. .L1ke-"reference numerals designate correcasing and communicating with the cam chamber is a cylinder 23 provided if desired with radiator ribs 24 while the head 25 of this cylinder is fomed with the usual intake passage 26 and valve 27 controlling the same and with the exhaust passage 28 and valve 29 therefor. The exhaust passage communicates with a suitable discharge 30 while the inlet passage 26 may be in communication with a carbureter asshown at 31 in Figure 2.

One side or head 32 of the casing 20 is provided with outwardly radiating ribs 33 supporting a bearing 34 for the driven shaft 35. At the opposite side of the casing a removable head 36 is secured thereto in any preferred manner and formed with radiating ribs 37 supporting the bearing 33 for the shaft. Secured upon this shaft is the usual fly wheel 39 having means indicated at 40 for connection with a starting crank or lever.

Within the cylinder 23 apiston 41 is disposed and may be either solid or tubular as shown. The lower end of this piston is formed with a skirt portion 42 providing bearings for the journal 43 of a friction roller 44 which is flanged at 45 and rides upon the periphery or actuating face of the cam 21.

This cam comprises opposite head portions forming a large cam 46 and a small cam 47,

'the former being provided with an apertured portion 49 inits web to properly balance the greater size'of the portion 46. The actuating L el 0 e ar 'er cam is c1 30sec a a fac 8 fthl ls lt greater distance from the shaft 35 than the similar face of the smaller cam 47.

The oppositeends of this cam' member are not only of greater length but also differ in thelr transverse wldth or diameter so as to provide side faces which m'a-y be located at different distances from a longitudinal central line extending through the axis of the cam which results in providing actuating faces at the sides ofthe cam differing in their are of curvature. r

Referring to Figures 2 and 3 it will be noted that on the larger ca-m head 46 the actuating face 50 at one side is at different distance from the central line 53 of the-cam and of a diflerent curvature from the opposite actuatingface 51 while the face 48 connecting these portions is of a curvature which effects the least movement of the pistonJ At the opposite or smaller cam head47 the 'face 52 1s at the greater distance from the central line 53 while thezface 5 1 is of less curvature and consequently nearer said line.

In order to insure a yielding contact between the piston roller and the'cam I have provided spring members which in order to secure a reduction in size and close nesting of the parts,are disposed at opposite sides of are. secured to the skirt by means of pins 57 extending through apertures 1n the arms to prevent rocking movement thereof and the clamping screws 58 extending through the arms into the piston skirt 42. The lower ends of these springs may be secured in any desired manner, for instanceby means of hooked lugs 59 bolted to the casing at 60. This novel'form of casing is also adapted to cooperate with the valve actuating members and for that purpose an intake cam" 61 is keyed to the shaft and operates upon a pusher 62 disposed in a tubular portion 63 of the casing and carries the rod 64- extended to the valve operating lever'65. I t i The exhaust cam 66 at'the opposite side of the casing is provided with a similar construction of parts for actuating the rocker lever for the exhaust valve 29. The casing is further providedwith an extension 67 at one side adapted to receivethe driving gear 68 for a generator or magneto disposed upon the platform 69 carried by the casing. This driving gear 68 is connected by the chain '70 with a sprocket gear 71 keyed to the shaft 35. l i

In the movement of the piston away froin its head while traversing the curvature of the controlling cam, it is' essential to provide suitable guide means to prevent side movement of the piston and this is effectually done by means of theparallel ribs 72 extended inward from opposite points on the casing, these ribs being formed with guide flanges 73 having suitable curved faces 74 whichforin a continuation of the cylinder walls atopposite points which permits a movement of the piston at all times in direct contact with the cam.

The general operation of theengine will be apparent from the foregoing description from which it will be seen that the larger-cam imparts to the piston its greatest length of stroke during the scavenging and suction cycles while the smaller cam head reduces the length of such stroke for and firing cycles.

As illustrating the variation of the timing in the piston movement, reference made to the diagram of Figure 3 from which it will be seen that the cam in its full line position the compression at the point 13.

'isfat the end of the firing stroke and about to begin the scavenging cycle. I In order to 1 illustrate the movement of agiven point on the camsuch as *thearrow atthe left, the cam has been surrounded; a circle having a series of equal divisions indicated by thenumorals 1 to16 inclusive, and it will be seen that the movement of the arrow from the position 1 to 2 causes a rapid inward movement of the piston equivalent to the space between;

1 and 2 indicated atthe upper portion ofthe diagram on the wall of thecylinder. This continues until the arrow reaches the point 3wh'en the portion of the cam ofless curvature is reached and t the speed of the: piston movement reduced so tliat ittravels a less distance in thecylinderbetween the points Sand 4 while when itreaches the point 5 of the circle it is atits greatest length of stroke and accomplishes a completescavenging action'of the cylinder.

The return or suction stroke begins in the 7 travel of the arrow'from the point 5'to the point 6, resulting in arelativelyslow move ment as indicated on't-heupper portion ofthe diagram and the wall 51 of the larger cam head bein got less curvature causes a rapid increase in this movement between the points 6 and 7, and 7 and 8, while at the point 9 the piston has reached the inmost limit'of its suction stroke, asindicated by dotted lines in Figure The movement from this time occurs at the smaller head and the face 52 thereof effects a gradual rising movement of t travel between the points 10,11 andt12 while thelimit of the short piston stroke is reached The return or firing action nowoccurs and there is a slow startingmovement in the travelbetween points'13'and'14 which ism teriallyincreaseddue to the, curvature of the face 54 so as to secure arapidsmovement during the firing stroke and the maximum, le- 1 verage up tothe point 16 after which the s pistoncomes to its inmost-point of travel at thepoint 1 and has completed the four cycles ofthe engine operation with proper provision ineach cycle for a variationin the speed of the piston so as to secure the most efiiciency.

incident to the dilferencegin curvature betweenthe opposite side'faces of each ofthe cam heads. 1 p n *It will be seen that 'thisassembla'ge'providesfor adirectaction of the piston upon V the cam and the control ofits movement thereby while the parts are so assembled as to greatlyreduce the weight and simplify the construction of the engine so that it can be quickly assembled and reassembled and comprises an operatingunit by which the core lated parts operate in unison to effect the intake and GXlliLllSlJ-flOl'Il the c'ylinder'and the actiontherefrom through the cam to the drive shaft. i i i While the detail construction of the several parts has been shown and described, the invention is not confined thereto as changes and alterations may be made without departing from the spirit of the invention as defined by the appended claims. 7

Having thus described my invention, what I claim as new and desire to secure by Letters Patentis Y 1. In a variable stroke engine including a cylinder and piston, a shaft, and a figure 8 cam disposed to actuate said piston and having heads of varied length to determine the stroke of the piston and its side faces at different curvature to control the timing oft-he opposite movements of said piston intermediate its limits of stroke.

2; In a variable stroke engine including a cylinder and piston, a shaft, a controlling cam upon said shaft operating in a path adjacent the open end of the cylinder, a piston disposed in said cylinder to directly engage said cam and having a skirt extending parallel to the cam, and oppositely disposed springs extending from the skirt of said piston to a fixed point.

3. In a variable stroke engine including a cylinder and piston, a shaft. a controlling cam upon said shaft, a piston disposed in said cylinder to directly engage said cam and having a skirt at opposite sides of the cam, and oppositely disposed springs extending from the skirt of said piston to a fixed point in planes parallel to that of the cam.

4. In a variable stroke engine including a cylinder and piston, a shaft, a piston within the cylinderprovided with an anti-friction member, a controlling cam upon said shaft disposed adjacent the open end of the cylinder in direct traversing contact with said member, spring supporting arms carried by the skirt of said piston and extending in opposite directions, and resilient members extending from said arms to a fixed point beyond said shaft.

5. In a variable stroke engine, a casing provided with a cam chamber, a shaft extending therethrough, a variable stroke cam disposed within said chamber, a cylinder extended from said chamber, a piston within said cylinder having engaging contact with the actuating face of said cam at the open end of the cylinder, a head for said cylinder pr0- videdwith inlet and exhaust valves, and actuating means upon said shaft for said valves.

6. In a variable stroke engine, a casing provided with a cam chamber, a shaft extending therethrough, a variable stroke cam disposed within said chamber, a cylinder extended from said chamber, a piston within cylinder having engaging contact with the actuating face-of said cam, a head for said cylinder provided with inlet and exhaust valves, actuating means upon said shaft for said valves, and tension means extending from the inner end of said cylinder to a point on the casing below said cam chamber and at opposite sides of the cam therein.

7. In a variable stroke en ine, a casing provided with a cam chamber, a shaft extending therethrough, a variable stroke cam disposed within said chamber, a cylinder extended from said chamber, a piston within said cylinder having engaging contact with the actuating face of said cam, a head for said cylinder provided with inlet and exhaust valves, actuating means upon said shaft for said valves, tension means "extending from the inner end of said cylinder to a point on the casing below said cam chamber and at opposite sides of the cam therein, an extension from said chamber provided with auxiliary driving means, means upon said shaft provided with a support, and means upon said shaft connected to actuate said auxiliary driving means.

S. In a variable stroke engine, a casing provided with a cam chamber, a shaft extending therethrough and carrying a variable stroke cam, a cylinder projected from said chamber, a piston therein disposed to directly engage said cam, and ribs projected inward from the casing within the cam chamber and having flanges forming a continuation of the walls of said cylinder for guiding said piston in its movement outward therefrom.

9. In a variable stroke engine, a casing provided with a cam chamber, and a cylinder projected therefrom, a shaft extending through said chamber and carrying a variable stroke cam, a piston within said cylinder having direct contact with said cam at the open end of the cylinder, a head for said cylinder provided with inlet and exhaust valves, opposite heads for said casing formed with shaft bearings and tubular passages, valve actuating cams disposed upon said shaft, and connections therefrom extending through said passages to the inlet and exhaust valves respectively.

In testimony whereof I aflix my signature.

ASA LEE RIGHTENOUR.

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