US2303838A - Mechanism for the interconversion of reciprocation and rotation - Google Patents

Description

Dec. 1, 1942. E. s. HALL 2,303,838

MECHANISM FOR THE INTERCONVERSION OF RECiPROCATION AND ROTATION Filed April 1 1942 2 Sheets-Sheet l I I L ZWWSMZ III/IIIIII I llIIll/ll/II771 Q 3 Q -m/ mm r K.

1, 1942. E. "s. HALL 2,303,838

MECHANISM FOR THE INTERCONVERSION -OF RECIPROCATION AND ROTATION Filed April 1, 1942 2 Sheets-Shet 2 Patented Dec. 1, 1942 I UNITED STATES PATENT OFFICE MECHANISM FOR, THE INTERCONVERSION F RECIPROCATION AND ROTATION Edwin S. Hall, Farmington, 00ml.- Application April 1, 1942, Serial N0. 437,159

. the shaft, and a wabbler as nonrotating, but

this may be illogical; Confusion may be avoided by using other terms. Herein a plate inclined to and rotating with the shaft is called by Michells term, slant, while a plate structure mounted on bearings on and inclined to the shaft, is called a connecting plate or conplate, since it serves to operablyconnect recipe rocating parts to the shaft, analogous to the conplate mechanism in which the operable connection between each reciper and the shaft in- 1 cludes a wristpin fastened'to the conplate arm connecting rods or .conrods in a cranlan' echanism. An object of this invention is to provide improved means for predetermining correctly the motion of a conplate.

also convenient to shorten reciprocating members to recipers, the term describing thefpartsor the assemblies whose motion is predominantly reciprocation along cylinder axes. A reciper may be a simple piston, but more often it is a more comprehensive. structure and may include a crosshead portion and one or two piston portions.

In most of theconplate mechanisms, the torque reaction from the-shaft is on the conplate which must therefore be held against rotation by substantial means. But the true motion of the Y '25 In discussing round engine mechanisms, it-1s.

with the axis of the pin substantially tangent to a circle concentric with and in the. plane of the conplate. All working surfacesof the conplate being surfaces of revolution relative to the conplate axis, or tangent thereto, practically no torque can be exerted on the conplate by the coacting parts, neglecting friction. The invention consists further of forming the ends of each wristpin substantially spherical and of providing internal surfaces in each reciper correctly formed to coact with the ends of the wristpins so that, together, they predetermine the conplate motion and maintain it geometrically cor-- rect.

In the drawings, Fig. 1 is an end view, partly in section, of a circle mechanism showing a true projection of the conplate in its inclined position on the shaft; Fig. '2 is a longitudinal section of the mechanism taken on the line 22 of Fig. 1;

Fig. '3 is ,a sectional view of the reciper and associated parts, taken on the line 3-3 of Fig. 2; and Fig. 4 is an analysis of the mechanism.

Referring to the drawings, shaft I0 is mounted for rotation in bearings M in cylinder blocks l5. fastened to shaft .10, and'conplate H is operably mounted between slants I6, the coacting bearing surfaces being spherical as shown, altho conplate is three-dimensional-a point on its mid-plane describes a spherical lemniscate, appearing in end view to rotate about a small circle at twice shaft speed and in the same sense. It is almost if not quite impossible to provide a conplate ,restraint capable of carrying the engine torque reaction while maintaining correct conplate motion. Any restraint which interferes with the true motion of the conplate, introduces serious vibrations and abnormal stresses. For example, if one part of the conplate is confined to move in a plane, the inertia efiects and extraordinary stresses introduced can destroy the mechanism. Objects of this invention are to avoid such diflicultiesby providing a conplate:

mechanism 'of such construction that,"wh ile the conplate transmits the turning effort from the recipers to theshaft, the conplate itself is practically free from torque; and further by providmg simple and practical control means for confining the ccnplate motion to that 'which is natural and geometrically correct.

Briefly described, the invention comprises a it is evident that any suitable bearirg construction may be used for mounting conplate II on shaft l0 so long as conplate II is operable upon shaft l0 and inclined thereto with the conplate and shaft axes intersecting substantially-in the mid-plane of conplate ll.

conplate II has as many arms as there are recipers I1. Each of the recipers l1 comprises one or two piston portions Nb and a crosshead portion l'lc. Pistons llb are operable in cylinders, formed in blocks l5, and crossheads "c are operable ,.in cylindrical'crosshead guides coaxial with the cylinders and formed in casing l2 The fixed parts of the machine, cylinder blocks 15 and easing I 2, are held together by bolts l3. 7

The operable connection between each reciper l1 and the arm of conplate ll includes wristpin l8, the axis of wristpin l8 being substantially tangent to a circle concentric with and in the plane of the conplate. The radius of the, circle,

the conplate arm radius, is such that the center of wristpin l8, during its normal movement, travels the same distance inside and outside the cylinder axis, 1. e. the wristpin center is the same distance inside the cylinder axis when the reciper is on center as shown in Fig. 2, as it would'be outside the cylinder axis if the reciper were at mid-stroke.

Slant members l6 are suitably keyed and- Associated with wristpin I8 is pinhead 20 which is operable in a bore thru crosshead He, the axis of this bore being perpendicular to that of wrist pin I8. Formerly the wristpin was fixed in or otherwise axially immovable relative to the pinhead in order to obtain the largest possible wristpin bearing area, the bearing being in the conplate arm. According to the present invention, the wristpin is adjustably fastened to the conplate arm, as by setscrew I9, but the bearing I8e to maintain the motion of conplate H always geometrically correct.

Wristpins I8 are axially adjustable relative to the arms of conplate II topermit them to accommodate errors in indexing of the several cyl inders orcrosshead guides or of the arms of conplate II. During assembly, one only of wristpins I8 may be secured by its setscrew I9, the other wristpins I8 being' set snugly enough to stay where they are leftby contacts with surfaces Ile while the mechanism is turned over. When each wristpin I8 is correctly adjusted axially relative to its arm of conplate II, all wristpins I8 are securely locked in correct position as bysetscrews I9.

In operation, rotation of shaft I and slants I6 causes conplate II to change the position of its plane without rotation of conplate relative to its own axis or the fixed parts I and I2 of the machine. The motion of wristpin I8 relative to the bore in pinhead 20, and of pinhead relative to .the bore in crosshead He, is in each case a combination of rotation and axial sliding. The conplate arm center which is the center of wristpin I8 moves in a path describing a lemniscate on the surface of a sphere, which path, in end view, iscircular, so that the ends We of wristpins I8 can contact successively surfaces IIe of recipers, II. As shown at F and G in Fig. 1, 0pposite ends I8e of two wristpins I8 are always (neglecting working clearance) in opposite contact with corresponding internal surfaces We of two recipers, so that conplate II cannot rotate in either direction. For clockwise rotation of shaft -I0 in Fig.1, contact Gis well begun, contact F is approaching its end, contact H is about to start, ready to take over the duty of contact F, and contact K has recently passed its job to contact G. Each contact. (or working proximity) occurs twice during each revolution of shaft III; with five arms on conplate II, there are twenty control contacts between wristpin ends I8e and internal reciper surfaces IIe during each revolution of shaft lo.

While each wristpin I8 constantly changes its angular relationship to the corresponding reciper II, if wristpin ends I8e are spherical about the center of wristpin I8, and control surfaces We are cylindrical over their length where contact this case is low because the conplate is practically free from torque.

To understand how little torque is on the conplate with this mechanism, and in general to understand the operation of the mechanism more completely, and especially how ends IOe of wristpins I8 coact with internal surfaces Me to predetermine correctly the motion of conplate II and to maintain it geometrically correct, reference is had to the analysis of Fig. 4.

conplate mechanism analysis when the z-axis intersects the reciper axis. a

shaft.

Views I, II, and III are the familiar end view,

' longitudinal section, and top or radial view, re-

spectively, and correspond to Figs. 1, 2, and 3 of the drawings.

Correct conplate motion is readily understood by plotting the locus of a point in'the conplate plane during operation of the mechanism. An easy way to plot three views of the locus of the conplate armor wristpincenter isto start with the conplate normal to the shaft, a position it never occupies in the mechanism, but one that is easy to draw. Ifthe conplate were normal to the shaft, a circle of radius 630 in-end view I.

' would contain all conplate arm centers An; and

occurs; the contacts will always be in the plane used to obtain somewhat broader contact than the point contact between a sphere and a cylinder of somewhat larger radius, altho the loading in in view II, the conplate would be represented by the y-axis. Divide the circle in end view I into a convenient number of equal sectors, project the points A0 tothe y-axis of view II, and swing the conplate into its actual position by rotatin its angle about the z-axis. Points A0 in end view I will move. vertically toward the z-axis, while their projections in view II swing thru arcs, and when projected back to view I, intersect the vertical lines at the points A.

The points A in end view I all fall on a true ellipse, the end view'of the conplate circle when the conplate is in its actual position inclined to the shaft. If the mechanism were running, the conditions shown at the several positions in view I would appear successively in any one position, generating the end view of the locus as shovm for the top cylinder position in view I. This end view of the locus" of conplate arm center A is a little circle of radius r, and the point A goes around the little circle at twice shaft speed.

radians/sec. angular velocity of the shaft axes.

The coordinates of conplate arm center A are:

=2VE sin =a sin 0 ys=h+r cos 20 za=r sin 20=2r sin 0 cos 0 From the foregoing, it is clearthat movement of the point A out of the plane of the cylinder and' shaft. axes during operation, is due to the inclination of the conplate, a constant quantity,

and not to any rotation of the conplate about its own axis. Rotation of the conplate about its own axis cannot be tolerated in a conplate mechanism becauseit would have to be oscillatory and would involve polar inertia efiects difficult to handle.

'- The essential characteristic of correct conplate motion is complete freedom from rotation of the conplate relative to its own axis and to the fixed Z T 1 /(h+r)4hr cos 0 Substituting and simplifying. the axial displacement of the reciper from mid-stroke position,

parts of the machine; The conplate must also be he a e e t o of the ec pe free from inertia torque, wherefore it must be in static and dynamic balance relative to its axis.

In the mechanism as shown in Figs. 1, 2, and 3, it is now more clear how ends We of wristpins l8, spherical about conplate arm centers A, coact a2 (M0 sin @{1 mal to the shaft, and draw at, at another cylinder position, A 0 being the angle thru which the z-axis has rotated bodily with the shaft, since it coincided with 0A0. Draw wristpin axis VoUo .L 6K0 and extend it to meet the z-axis at Z. Project the points Ao, V0, and U0 to the y-axis of view II and give the conplate its inclination as before, locating the lines VAU in views I and II, the

projections of the wristpin axis in its actual position for 4 0'as shown. 1 In view I, Wextended mustalso intersect the z-axis at Z. Hi extended intersects the e-axis at M. A AQCA=20. Projection CE makes an angl of deviation, A GOA: A 1/ with-trace GT5 of the plane of the cylinder and In the mechanism, the 'p inhead axis always in tersects the cylinder axis at right angles and is therefore parallel to the y-z plane and shows true length in view I. The pinhead axis also intersects the wristpin axis at right angles, and will therefore appear I V U' in view I. 'Draw pinheadaxis 63 .L To at J and making 4 v with expressions, leaving them much simplified. These expressions hold only for the conplate mechanism having wristpins tangent to the conplate circle and correctly predetermined conplate motion. 7

If the axial movement of the reciperv were har- I monic, the axially directed inertia forces of n recipers, each the product of its effective reciprocating mass m and its acceleration, would combine to form an inertia couple about the z-axis of magnitude:

Actually, because the' reciper motion departs slightly from harmonic, the magnitude is about 1.4% larger, but it is within .001% of being contrace E6 of the plane of the cylinder and shaft cylinder now being considered can also be located in views II and III.

The displacement of the reciper from midstroke where 0:0, is the same as that of the pinstant for any given shaft speed, so that it can be balanced by counterweights capable of producing an equal and opposite centrifugal couple, in a well-known manner,'the dynamic balance of this conplate mechanism being practically as perfect as that ofthe Michell slant-slipper mechanism In addition to axial movement, the reciper in the conplate mechanismhas a little oscillatory rotation, tending to maintain pistons ringswfree.

The angle of deviation of the conplate arm radius from the plane of. the cylinder and shaft axes,

z a: .4 C011 The angle of reciper rotation,

A v= LOCJ= 4 am Sin 2r sin cos 0 7 /(h+r)4hr cos 0 (h-l-r)2r cos 0 cos "1/ h +'T) -4hr'e6s o The reciper rotates against shaft rotation while passing mid-stroke; and the reciper rotates with shaft rotation while going over center.

The angular velocity of the reciper,

By solving when '7 is maximum, and

r 'y, .=arc SlIl-E I The angular acceleration of the reciper,

The inertia torque of the reciper,

T1=(polar moment; of inertia of reciper) X (angular acceleration of reciper) (all dimensions in'inches; g.=386 in./sec.

W=wght. of reciper K=radius of gyratiorr of reciper tion relative 'to the axis of the cylinder and crosshead. Projections fromvthe end view I to auxiliary view IV must be made. .L VTJ' and parallel to pinhead axis in end view I. 7

With center at A and radius AoVo, arcs intersects projections from V and U at V and U' respectively. VU intersects projection from C and J of view I at J "=end view of pinhead axis.

In view IV the trace of the yplane inter--.

sects wristpinjL'U' extended, at Z so that ii is parallel to N. m and m: are the same respectively in both views II and'IV.

The projection from O in view I intersects the trace of the Z]Z plane in view IV at 0'. Since vi'ew IV is parallel to the wristpin axis, the projection of onplate radius 6'1 in view IV must be .I. V'U', and must intersect the trace of the 11-2 plane at O. The A OO'A= Since view IV is parallel to the cylinder axis, the resultant reciper thrust P can be shown as a vector applied to the pinhead axis at J. The component of P normal 'to the wristpin, P sec or, is applied to the conplate and causes the loading on the conplate bearings. The component P tan a defines the turning effort and is equal to the torque reaction of the reciper crosshead against its cylindrical guide.

View V is drawn on a plane .1. wristpin axis V'U'. All projections from view IV to view V are made parallel to V'U'. Points A and J are the same in view V. ,Conplate radius O'A', is parallel to the plane of view V and therefore shows its true length. With center at A in view V, and radius 65=b=(h+r),, the projection in V of O in view IV is intersected at O in view V, defining the angle 6.

The torque on the shaft arising from resultant reciper thrust P is equal to the torque reaction of the crosshead upon its cylindrical guide:

T,=Ptan a- (h+r) cos e+Ptan (1-67: Ptan whCOS'Y Pa 005 207 -11 cos 0) if the fraction be neglected, the value of the fraction being always very nearly 1, varying from To find the torque on the conplate, arising from resultant reciper thrust P, view VI is drawn parallel to the plane of the conplate. For convenience in interpretation of view VI, it is repeated at the left of Fig. 4 in correct relationship to' view II. The force component in the conplate plane, tending to turn the conplate about its axis, is the component parallel to the conplate radius OA',

P sec a sin e and its moment arm is AJ' from view IV. The torque on the conplate 4hT' 7l7(h+7) sin 0 cos 0 =Pa cos 0 The torque on the conplate is always small, as can be seen from the ratio of torque on the conplate to torque on the shaft:

Z Pa cos 0 ab sin 0 T, Pa cos (:l(2hb'a cos 0) (ba cos 6) =.000 to .054=.025 in summation in a mechanism of usual proporcomponents act outwardly, they tend to uncenter the conplate and would make its motion unstable and its operation noisy if no control of the conplate motion were provided. The inwardly acting components predominate whenever the summation of cylinder pressures is greater than that of the reciper inertia forces. Thus when a conplate engine is running normally under load, the inwardly-acting components. tending to center the conplate, would permit it to run quietly even if no conplate control were provided. However, when reciper inertia forces are greater in summation than the cylinder pressures, as when the shaft overruns the recipers, the outwardly-acting components predominate, and control of the conplate motion is iiecessary.

Inproviding a conplate mechanism in which the conplate is practically free from torque, to-

g'ether with simple and practical controlmeans for maintaining the conplate motion geometri-' cally correct, as shown and described, it is apparent that the objects of this invention as stated have been attained. While a particular conof and concentric with said conplate,means oper- I ably connecting said wristpins and said recipers, and means for predetermining the geometrically correct movement of said conplate and including surfaces substantially coaxial with said recipers and coacting with the ends of said wristpins.

4. In a machine of the class described, a shaft, a frame and bearings in said frame operably supporting said shaft, cylinders in said frame parallel to said shaft, recipers reciprocable in said cylinders, and mechanism operably connecting said shaft and said recipers, said mechanism including a conplate operably mounted on and inclined to said shaft, wristpins securely fastened tosaid conplate with their axes substantially tangent to a circle in the plane of and concentric with said conplate, and means coacting with the ends of said wristpins for maintaining the motion of said conplate geometrically correct.

5. In a machine of the class described, a shaft, a frame and bearings in said frame operably supporting said shaft, cylindrical crosshead guides in said frame and parallel to said shaft, recipers including crosshead portions reciprocable in said cylindrical crosshead guides, and mechanism operably connecting said shaft and said recipers,

said mechanism including a conplate operably mounted on and inclined to said shaft, wristpins securely fastened to said conplate with their axes substantially tangent to a circle in the plane of and concentric with said conplate, means operably connecting said wristpins and said crosshead portions of said recipers, and surfaces in said crosshead portions coacting with the ends of said wristpins for maintaining the motion of said conplate geometrically correct.

6. In a machine of the class described, a shaft, recipers reciprocable parallel thereto, and mechanism operably connecting said shaft and said reoperably mounted on and inclined to said shaft,

wristpinsadjustably fastened to said conplate with their axes substantially tangent to a circle in the plane ofand concentric'with said conplate, pinheads operably connecting said wristpins andsaid recipers, and surfaces in and substantially coaxial with said recipers coacting with the ends of said wristpins to control the motion of said swashplate. a

2. In a machine of the class described, a shaft, recipers reciprocable parallel thereto, and mechanism operably connecting said shaft and said recipers, said mechanism including a conplate operably mounted on and inclined to said shaft, an arm on said conplat for each of said recipers, a wristpin fastened to each of said arms with its axis substantially tangent to a circle in the plane of and concentric with said conplate, a pinhead and a bore in said pinhead operably receiving said wristpin, another bore in each of said recipers operably receiving said pinhead, the axes of said bores being perpendicular to each other, and means for maintaining the motion of .said conplate geometrically correct, said means arm on said conplate for each of-said recipers, a

wristpin fastened to each of said arms with its axis substantially tangent to a circle in the plane cipers, said mechanism including a conplate operably mounted on and inclined to said shaft, wristpins with their axes substantially tangent to a circle in the plane of and concentric with said conplate, and means associated with said wristpins for maintaining the motion of said conplate aa=a sin 0 ya=h+r cos 20 zx=r sin 20 the several quantities as defined in the specifica tion.

7. In a machine of the class described, a shaft,

recipers reciprocable parallel thereto, and mechanism operably connecting said shaft and said recipers, said mechanism including a conplate operably mounted on and inclined to said shaft, wristpins securely fastened to said conplatewith their axes substantially tangent to a circle in the plane of and concentric with said conplate, and means for defining the motion of said recipers so that the displacement of eachreciper from midstroke position is:

C it cos 0 zJ=a Sm l 2 (b -ea cos 6)! the several quantities as defined in the specification. I

8. Ina machine of the class described, a shaft, recipers reciprocable parallel thereto, and mech- "anism operablyconnecting said shaft and said axes substantially tangent to a circle in the plane of and concentric with said conplate, and means for defining the motion ofsaid recipers so that the velocity of each reciper is:

2 2b +3b cos -11 cos 0} the several quantities as defined in the specification.

9. In a machine of the class described, a shaft, recipers reciprocable parallel thereto, and mechanism operably connecting said shaft and said recipers, said mechanism including a conplate operably mounted on'and inclined to said shaft} wristpins with their axes substantially tangent to a circle in the plane of and concentric with said conplate, and means associated with said wristpins for defining the motion of said recipers so that the acceleration of each reciperis:

2 2 %f= aw sin 0{1+% the several quantities as defined in the specification. p

10. In a machine of the class described, a shaft,

recipers reeiprocable parallel thereto, and mechanism operably connecting said shaft and said recipers, said mechanism including a conplate operably mounted on and inclined to said shaft, and operable connections between said conplate and said. recipers sq constructed and arranged that the motion of said conplate is predetermined and the .torque on said conplate arising from reciper thrust P is:

that the motion of said conplate is predetermined and the ratio of the torque on saidconplate arising from reciper thrust P and the torque on said shaft arising from reciper thrust P is:

T, (2hb,-a cos 0) (12 -11 cos 0) 5% in summation the several quantities as defined in the specification. i

12. A rocker-mechanism comprising a shaft, 2. conplate operably mounted on and inclined to said shaft, recipers reciprocableparallel to said shaft, and operable connections between each' 13. In a machine of the class described, a shaft, a frame and bearings therein operably supporting said shaft, cylinders disposed about and parallel to said shaft,'cylindrical crosshead guides coaxial with said cylinders, recipers including piston portions and crosshead portions operable in said cylinders and crosshead guides respectively, and mechanism operably connecting the crosshead portions of said recipers with said shaft, said mechanism including a conplate operably mountedon and inclined to said shaft and a conplate arm assembly operably connecting said conplate with each of said crosshead portions of said recipers, said assembly including working surfaces essentially tangential to circles parallel to the plane of said conplate (thereby avoiding direct application of working loads to produce .torque on said conplate) and control surfaces substantially radial to the plane of said conplate, at least two of said control surfaces being always in working proximity to two of said recipers (to prevent rotation of said conplate relative to said frame and to maintain the motion of said conplate geometrically correct).

14. In a machine of the class described, a shaft,

aframe and bearings therein operably supporting said shaft, cylinders disposed about and parallel to said shaft, recipers operable in saidcylinders, and mechanism operably connecting said recipers to said shaft, said mechanism comprising a conplate assembly including a conplate operably mounted on and inclined to said shaft, working surfaces in said assembly substantially tangent to circles parallel to the plane of said assembly (thereby avoiding direct application of working loads to produce torque on said conplate), and control surfaces in said assembly substantially radial to the plane of said conplate and contacting said recipers successively (to prevent rotation of said conplate relative to said frame and to maintain the motion of said conplate geometrically correct).

15. In a machine of the class described, a shaft, a frame and bearings therein operably supporting said shaft, cylindrical surfaces in said frame disposed about and parallel to said shaft, recipers operable in said cylindrical surfaces, a conplate operably mounted on and in'clined'to said shaft, arms on said conplate, and means operably con.-'

,necting said arms with said recipers and including attachments on said arms, at least two of said attachments be ing always in opposite working proximity to two of said recipers to prevent rotation of said conplate relative to said frame and to maintain the motion of said conplate geometrically correct.

16. In mechanism of the class described, a shaft, a conplate operably mounted on said shaft and inclined thereto, reciprocating embers op-, erable parallel to said shaft, and means operably connecting each of said reciprocating members with said conplate, said means including an arm on said conplate, a wristpin with its axis held substantially tangential to a circle concentric with and in the plane of said conplate, said wristpin operably engaging said reciprocating members during operation, and means for adjusting said wristpin axially and for locking said wristpin securely upon said arm.

, EDWIN S. HALL.

Certificate of Correction Patent No. 2,303,838. December 1, 1942.

EDWIN S. HALL It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows: Page 2, second column, line 59, for its read it; page 4, second column, line 2, in the equation, for AOOA read LOOA page 5, first column, line 50, claim 1, for swashplate read c'onplate; page 6, first column, line 57, claim 12, for rocker read conplate; and in the drawings, Sheet 2,

'Figure 4, upper left-hand corner thereof, for COMPLATE AXIS read OONPLATE AXIS; and that the said Letters Patent should be read With these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 1st day of June, A. D. 1943.

[SEAL] HENRY VAN ARSDALE,

Acting Commissioner of Patents

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