US3034362A

US3034362A - Crank actuated means for retaining fluid pressure at top center

Info

Publication number: US3034362A
Application number: US44499A
Authority: US
Inventors: Alfred M Caddell
Original assignee: Individual
Current assignee: Individual
Priority date: 1960-07-21
Filing date: 1960-07-21
Publication date: 1962-05-15
Anticipated expiration: 1979-05-15

Description

y 1962 A. M. CADDELL 3 CRANK ACTUATED MEANS FOR RETAINING FLUID PRESSURE AT TOP CENTER Filed July 21, 1960 2 Sheets-Sheet 1 FIGJ A. M. CADDELL CRANK ACTUATED MEANS FOR RETAINING FLUID May 15, 1962 PRESSURE AT TOP CENTER 2 Sheets-Sheet 2 Filed July 21, 1960 St res are Unite This invention is applicable to reciprocating engines and similar moving mechanisms wherein the timing of fluid pressure release greatly affects operating efficiency. Described herein is an arrangement featuring a shell structure open at its top and bottom, which structure telescopes anti-frictionally within a piston, the shell providing a housing and aligning means wherein a floating wrist pin pivotally supports a connecting rod formation that responds to the throw of the crank assembly to which it is movably secured.

The objects of this invention are to retain maximum pressure in a motive fluid between a cylinder head and the head of the piston until the pin of the crank assembly reaches an advanced position on the power stroke where the angle of the crank arm permits a small amount of fluid under pressure to do a maximum amount of work; after which advanced position the motive fiuid is gradually and then wholly released to take advantage of everincreasing leverage up to the 90-degree position of the cycle. At present, combustion pressure in a cylinder is timed to be the greatest at top center of the crankthrow Where leverage is non-existent, the lag of the combustion pressure only being converted into work,

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while the travel of the piston itself is temporarily haltedbetween top center and said advanced position, the crankpin contiues uninterruptedly throughout its cycle. Whereupon, after the crankpin passes the aforesaid advanced position, the piston assembly starts downwardly in its travel under full expansion pressure of the motive fluid throughout the most favorable leverage range on the power strokethat is, commencing" from the 25, 30 or Second, to prevent engine vibration caused mainly by a anti-leverage firing of the fuel-air mixture in an internal combustion engine or, if the motive fluid is steam, delaying application of pressure until a more favorable leverage position in the cycle has been reached to permit the steam to exert maximum turning effort at the crankshaft before cut-0E.

Third, to obtain a prescribed power output at greatly reduced r.p.m. compared to the r.p.m. now required and thus achieve a very considerable saving in fuel.

Fourth, to make available a piston assembly that functions as a'single unit and a connecting rod formation that transmits energy to the crankshaft at the most favorable leverage application.

An elongated branch of the rod formation is fulcr'umed around the aforesaid floating wrist pin in the shell and on its other end is movably secured to the crankpin by conventional bearing means. An integrated arm of this formation extends right angularly a prescribed distance from the wrist pin to bring about in response to the movement of the elongated branch an arcuate length of travel. The connecting rod formation functions, as follows:

Upon said piston reaching its maximum travel heighth in its cylinder, which is also represented by top center of the crankthrow, the integrated arm extends 90 degrees from the center line that runs through the crankshaft, the crankpin and the wrist pin. Therefore, when the crankpin moves in'its cycle from this center line, the arm commences its arcuate swings. Obviously, the greater the length of the 'arm and the greater the radius of the crankthrow, the greater the arms arcurate travel will be. 'During this travel, the piston and the motive fluid will remain at the same heighth in the cylinder, or chamber, that obtained before the movement of the crankpin from top center and will so remain until the crankpin passes a prescribed advanced position on the power stroke. This position may be 25, 30 or 35 degrees past top center, again all depending on the length of the integrated arm, and the radius of the crankthrow. Thus,

35-degree position instead of from the zero leverage position at top center, as at present.

At this juncture, it should be stated that a slave arm is also fulcrumed around the wrist pin, extending an equal distance right angularly in the direction opposite to that of the integrated arm, thus providinga corresponding offset or arcuate length of travel on the opposite side of the wrist pin. Hence, when the piston is at top or bottom center, this connecting rod formation assumes the shape of a T. Both the integrated and the slave arms are connected by movable tie-bars to the top wall of the piston.

The integrated arm is fitted with a driving gear that transmits through intermediary pinions reverse motions to a driven gear installed in the fulcrumed section of the slave arm, said driving and driven gears being mounted concentrically around the wrist pin. Balanced power effects are thus obtained, both arms working in unison according to the dictates of the crankthrow to maintain the heighth of the piston in the cylinder throughout the aforesaid number of degrees on the power stroke.

Reverting for a moment to the aforesaid anti-leverage firing of the fuel-air mixture in an internal combustion engine:

In conventional engines, especially the aviation type, the fuel-air mixture is ignited a number of degrees be 7 fore the crankpin reaches top center so that combustion pressure will build up to its maximum at the point of maximum compression pressure, which occurs when the crankpin is at top center of the crankthrow. The momentum of the crank assembly carries the revolving mechanism past this top center, whereupon the lag of the combustion pressure, and the lag only, results in the development of turning effort at the crankshaft. However, due to lack of leverage, much of the initial force resulting from the explosion of the gases is dissipated via the connecting rod to the crankshaft, causing purposeless pounding and setting up intense vibrations. This condition continues for a number of degrees past top center and it is not until the crankthrow is well under way that the influence of leverage becomes responsible for the development of torque.

The requirement of firing the mixture before the piston reaches top center is due to the comparative slowness of flame travel compared to that of piston travel. Although the time period involved is infinitesimally small, the difference in power output due to advanced firing or alternate retarded firing is overwhelmingly great. i

As an instance of said comparative slowness, in an aviation engine having a 6-inch bore and ignition taking place 30 degrees before top center, the flame travels from the igniter across the bore through said, 30 degrees to top center ata speed of approximately feet per second; which, as will be observed by checking the following table, is considerably slower than that of the speed of travel of the piston throughout the same number of degrees.

Bearing in mind that the travel speed of a piston varies due to reversal of motion at top and at bottom centers between minimum and maximum, this table is presented simply to focus attention on the speed of the crankpins travel per se, which is constant for any given throttle setting.

- Crankshaft Revolutions per Minute 7 Among other features, this prevent the build-up of rings being forced inwardly in ings are also installed .in' the walls side-thrust friction down sumes an oppositely inclined position.

. branch at the 270-degree position of the cycle.

Crankshaft Revolutions per Second .00555/sec. .00417/500.

.00208/see. .0Dl65/sec.

Revolution the integrated and the slave arms in neutral-positions relative .to the crankshaft, crankpin and wrist pin center .00377/see.

Which micro-second periods of time focus attention on build-up and the aforesaid speeds of crankpin rotation.

To obtain maximum benefits from this invention, it is proposed to employ an oblong-shaped piston somewhat on the order of that described in pending application Four- Sided Piston and Fluid Sealing Means, Serial No. 782,453. form of construction permits roller bearings to be installed in the piston for contacting the walls of a correspondingly shaped chamber and thus power-consuming friction.

In this connection it has thrust'pressure' is one of the major plagues of engine operation, serious friction developing reactively between the piston and its cylinder. Inasmuch as round pistons and cylinders prevail'in'present-day engine practice, the side of the piston that absorbsthe thrust of the crankthrow rubs especially hard against the cylinder wall, the their grooves. This results during every power stroke, in

into many thousands of feet per minute. As an indicathat of an engine turning at 1,500 r .p.m.; rather, it is four or more times as great. V

In the presently described piston assembly, rollerbearof theshell structure to contact the inner wallsof the piston, thus keeping to the barest minimum.

Other features offered by this inventionwill become apparent as the herein-description proceeds.

In the drawings:

FIG. 1 is a cross-sectional View of a chamber and the the piston travel mounting tion of the losses thus created, the friction developed in an engine operating at 3,000 r.p.m. is not just double piston assembly mounted therein; also shown is the pivotal arm assembly and the connecting tie-bar linkage between the shell and the piston. This figure shows the pivotal assembly in neutral position, the arms thereof being at exact right angles to the center line extending through the crankshaft, the crankpin and the wrist pin of theshell.

FIG. 2 shows the crankpin at the 3Gdegree-past-topcenter position and the correspondingright angular positions of the integrated and slave arms, the progressive elevations of said arms during the crankthrow causing retention of the piston and motive fluid at its maximum heighth in the chamber. Being coupled via the wrist pinto the crank assembly, the position of the shell in this figure, compared to the position shown in FIG. 1, haschanged relative to that of the piston which, due to thearc'uate travel of the arms, has remained at top center. travel the combustion area between the tops of the piston and'the cylinder heads in FIGS. 1 and 2 remains the same.

FIG. 3 shows the position of the piston at 90 degrees past top center, theiintegrated pivotal arm at this position being at an exact right angle to the center line between the wrist and the, crankpins'while the slave arm, due to reverse action gearing in the fulcrum area, as-

It will be noted, too, that due to this arcuate V This view also showing to each of the arms and a space provided for pinions motion of the slave arm will therebetween so that the be reversed by said pinions. 7

FIG. 7 is a view of an individualtie-bar showing the lightening opening in the central section thereof and the holes for accommodating the insertion of pins that movaly connect the shell to the piston.

FIG. 8 is an enlarged View of the pivotal arm assembly only, showing the access cover plates of both the fulcrumed area and the arms,and a partially exposed view of the intermediary pinions and the driving gear that meshes therewith. The driven gear of the slave arm is not shown in this view. I

FIG. 9 is an enlarged partial cross-sectional end view taken on the line 9-9,FIG. 5 showing in dotted outline the linkage pins extending transversely through the piston and through the shell. r a

FIG. 10 is an end view of the gear box showing the driving gear secured to the integrated arm of the pivotal arm assembly and meshing with pinion gears to cause reverse motion of the driven gear secured to the slave arm.

FIG. 11 is an enlarged three-quarter view of the shell structure only, showing the roller bearings protruding from the sides thereof for contacting the inner wall of the piston and thus preserve anti-frictional alignment of said shell.

Numeral 1' represents the oblong chamber, ordinarily called a cylinder, of an engine. The piston is designated 2, the shell 3, the long branch of the pivotal arm 4 and the integrated branch thereof 4A, while the slave arm is indicated by 43. Tie-bar 5 connects the shell to the piston, the lightening opening therethrough being identified as 5A. (Tonnection between the shell and the piston is made possible by linkage pins 6. i

The oblong piston is shown in the several views in its longer-side dimension. To prevent blow-by of the motive fluid in combustion chamber 26, compression bars 7 are Shell 3 likewise carries roller bearings indicated by 9 in its walls to reduce to a minimum theside-thrust friction that develops during engine operation. Such roller bearing mounting, takenin conjunction with the roller bearings maintaining contact between piston 2 and chamber 1, assures anti-frictional operation and making more energy' available for work at the crankshaft.

Crankpin'lt) is shown at top center 25 of the crankthrow, FIG. 1, and at 30 degrees past top center in FIG. 2; at degrees in FIG. 3 and 270 degrees in dottedoutline and at degrees in FIG. 4. Crankshaft 11 is connected by crankarm 12 to crankpin 10. Balance weights 13 are secured to crankarms 12 by screw bolts 14.

Wrist pin 15 becomes the fulcrum for the pivotal arm assembly which is, mounted therearound by means of bearing assemblies 4 and in FIGS. 5

16, shown exposed in FIGS. 1 through and 8. Separate covers 17, removably secured to piston 3 by a plurality of screw bolts 17A,

are provided to permit access to

gears

18 and 19 secured respectively to the integrated and the slave arms of the assembly by bolts 24. The shaftsofpinions 20, FIGS. 8 and 10, are cradled in bearing assemblies 21. 'As aforesaid, power applied by driving gear 18 is transmitted by these pinions to gear 19, thereby causing a reverse motion and enabling slave arm dB to function simultaneously and just as effectively as integrated branch 4A in maintaining the relation between the arm assembly and piston 2.

It will be noted that by means of tie-bars 5 and pins 6, positive relation between the arm assembly and the piston is maintained at all times during the reciprocating travel of the piston.

As shown in FIG. 8, covers 22, which are secured to shell 3 by a plurality of screw bolts 23, permit access to the interior of the arms.

The tie-bars 5 function within the confines of piston 2 and shell 3, pins 6 extending through the piston and the shell walls on each side thereof. Pins 6 have a removable cap 6A on one of its ends, which cap is locked in position by a pin 6C, shown in FIG. 9.

Having described my invention, I claim:

l. The combination with a rotatable crank assembly and a piston assembly reciprocated thereby, of a connecting rod formation operatively connected to each of said assemblies, said piston assembly having an outer structure and an inner shell structure that has a wristpin extending transversely therethrough, said formation being pivotally mounted around said wristpin, an elongated branch of said formation, an arm merging with and integrated on the piston end of said branch and extending outwardly at a right angle thereto, a slave arm that extends a like distance from the opposite side of said wristpin at a righttangle to said branch, means connecting said slave arm with said integrated arm to obtain travel movements that correspond directionally with each other, linkage means at the extremity of each of said arms for establishing connection with said outer structure and transmitting thereto the length of arcuate motions induced by the motions of said elongated branch.

2. The combination with a rotatable crank assembly and a piston assembly reciprocated thereby, of a connecting rod formation operatively connecting said assemblies, said piston assembly having an outer body and an inner body comprising a shell adapted to travel reciprocally within the outer body, a wn'stpin positioned transversely through the sides of said shell, said connecting rod formation being comprised of an elongated branch, an integrated arm that extends at a right angle thereto and a slave arm having a length equal to that of said integrated arm and mounted oppositely therefrom, said formation being pivotally fulcrumed around said wristpin, a driving gear positioned around said wristpin and secured to said integrated arm and a driven gear positioned around said wristpin and secured to said slave arm, a plurality of pinions mounted between said gears and meshing therewith to provide arcuate lengths of travel in said slave arm opposite to arcuate lengths of travel induced in said integrated arm by the rotation of said crank assembly.

3. The combination with a rotatable crank assembly and a piston assembly reciprocated thereby, of a connecting rod formation operatively connecting said assemblies, said piston assembly having an outer structure capped by a top and an inner shell structure open at its top and bottom and having a wristpin floatingly mounted and extending transversely through its sides, said connecting rod formation being comprised of an elongated branch, an integrated arm extending at a right angle from one side of said branch and a slave arm extending a like distance from the opposite side of said branch, said formation being pivotally mounted around said wristpin, gear means positioned around said Wristpin within said formation to transmit motion induced in said integrated arm by said rotatable crank assembly' to said slave arm, linkage means of equal length connecting each of said arms at their extremities to the top of said outer structure for transmitting the length of equalized arcuate motions of said arms thereto.

4. The combination with a rotatable crank assembly and a piston assembly reciprocated thereby, of a connecting rod formation operatively connecting said assemblies, said piston assembly having an outer structure capped with a top and an inner structure comprising a shell adapted to undergo reciprocal travel within said outer structure, a wristpin floatingly mounted to extend transversely through the sides of said shell, said connecting rod formation being comprised of an elongated branch having connection on one end with said crank assembly, an integrated arm extending at a right angle on one side of said branch and a slave arm extending a like distance from the opposite side of said branch, said formation being pivotally mounted around said Wristpin on the end of the formation opposite said crank assembly, gearing within said formation positioned around said wristpin, said gearing being adapted to transmit arcuate motions induced in said integrated arm by said rotatable crank assembly to said'slave arm, linkage means connecting each of said arms to the top of said outer structure for transmitting simultaneously thereto the length of the arcuate motions of said arms, bearings mounted in the sides of said shell for making anti-frictional contact with the inner wall of said outer structure during the shells reciprocal travel therewithin.

5. The combination with a rotatable crank assembly and a piston assembly reciprocated thereby, of a connecting rod formation operatively connecting said assemblies, said piston assembly being comprised of an outer structure having a top and an inner structure comprising a shell adapted to undergo reciprocal travel within said outer structure, a wristpin extending transversely through the sides of said shell, said connecting rod formation having an elongated branch movably secured to said crank assembly, an integrated arm extending at a right angle on one side of said branch and a slave arm positioned on the side of said branch opposite said integrated arm and being responsive to the motions thereof, said formation being pivotally mounted around said wristpin for responding to the swings of said elongated branch, linkage means connecting each of said arms to the top of said piston, a crankpin in said crank assembly establishing a crankthrow during its rotation, a top center of said crankthrow, said arms commencing their arcuate travel upon the arrival of the crankpin at said top center and thereafter lending their length of travel to said piston assembly.

References Cited in the file of this patent UNITED STATES PATENTS 1,379,115 Mallory May 24, 1921 1,420,236 Bohman June 20, 1922 1,430,491 Calcaterra et a1. Sept. 26, 1922 1,431,617 Young Oct. 10, 1922