US2636392A - Wobbler drive mechanisms - Google Patents

Description

April 28, 1953 E. K.`sPARMANN woBBLER DRIVE: MECHANIsMs 3 Sheets-Sheet 1 Filed June 8, 1949 FIG. 1A

FIG. 1

IIIIIIIII-llll lilllllllllll INVENTo ,EDMom ERNST KARL SPARMANN ATTORMY April 28 1953 E. E. x. sPARMANN 2,636,392

woBBLER DRIVE MEcHANIsMs Filed June 8, 1949 3 Sheets-Sheet 2 FIG. 2 FIG. 3

v INVENTOR. EDMQND ERNST KARL sPARMAm M46; f ATTORNEY April 2s, 195s Filed June 8, 1949 '5. E. K. SPARMANN woBBLER DRIVE MECHANIsMs '3 sheets-sheet s INVENTOR.l EDMOND ERNST KARL SPARMANN ATTORNEY Patented Apr. 28, 1953 WOBBLER DRIVE IVIECHANISMSl Edmund Ernst Karl Sparmann, Stockholm, Sweden Application June 8, 1949, Serial No. 97,884 In Sweden June 8, 1%4'8 13 Clainls.

The present invention relates to improvements in piston engines having at least two pairs of pistons running in individual cylinders generally arranged circumferentially around the engine shaft which is parallel with the axis of the cylinders. The invention is of particular interest in such engines in which the cylinders in each pair have opposed Working strokes and are interconnected by piston rods coupled to a non-- rotatable wobbler body which is rotatably but non-displaceably journaled on the engine shaft. Thanks to their compact design such engines permit a considerable reduction of the external dimensions and constructional weight for the same engine output as compared with piston engnes of conventional designs. One of the most important of the several problems appertaining to such motive power` engines or Working engines, such as compressors, pumps etc., with wobbler drive, concerns the suitable design ci the mechanism for power and motion transmission between the reciprocating working pistons travelling in paths parallel with the engine shaft and the periphery of the wobbler plate. An object of the present invention is to give a practical solution of this particular problem so that the inanifold and important advantages aimded by the logical application of the wobbler plate principle, in addition to those already named, can be realised.

Due to the somewhat complicated three-dimensional. paths of movement resembling lemniscate motions described by a point situated on the periphery of the Wobblerplate. the task is rendered particularly coupling' between each piston and the wobbler plate must, on this account, possess live deg-rees of' freedom, and at the same time be ablev to hear the stresses iin-.- posed which in high speed. intern-al combustion engines having high compression reach considerable magnitudes. An additional and very important requirement must be met in this respect, i, e. that movements oi the reciprocating masses; such as pistons, piston rods, etc., .rust be as equivalen-t or so-called harmonic oscillations as possible, so that a complete dynamic counterbalancing of the engine shall be attainable. Finally it is imperative for the complete realisa tion of several of the most important advantages of the wobbler plate principle, that two. pistons can at the same time-be attached. to: each attachment point on the periphery oi thewobbler plate, namely one on each side of the so-called wobbler plate-y plane..

While usingsimple constructiona-l elements already well tried in the art, the present invention has been developed with a View tobring about a fully satisfactory .solution oi this important particular problem for wobbler plate engines from a theoretical and practical View point. The invention is substantially characterized in that said piston rods are interconnected by a knee action unit bendable only in a rst plane including the commu axis of the pair of cylinders, said unit including a coupling element upon which said connecting rods are journalled s0 as to be swingable only in said rst plane and to be displaceable without rotation in a second plane perpendicular thereto, said coupling element being pivoted on said wobbler body so as to be rotatable in relation thereto about an axis extending in the wobbler plate plane.

The idea of the invention can be realised in a multitude of different embodiments and some characteristic examples are diagrammatically illustrated by the accompanying drawings. All ci the parts not necessary for the illustration of the present invention have been omitted from the drawings for sake of elearness.

Fig. 1 is a lateral view partly in section showing,J an example or' piston connecting. mechanism embodying the invention.

Fig. 1A is a fragmentary section similar to the left hand portion of Fig. 1 showing a diiiferent form. o'. the pis-ton connecting mechanism.

Fig. 2 shows a detail of the construction shown in Fig. LA, namely the coupling together of the big-ends of the two piston rods to a knee action unit Elige. 3, 4. and 5 sho-w one of thev coupling elements of the mechanism used in Figs. 1, 6, 'Z and 8 three different projections, partly in section.

Figs, 6.r 7 and 8 show a wider variant oi. the ideay of the invention in various projections, and in various positionsFig.. 6 at a dead centre position and partly in axial section and Fiss. 7 and the same variantv of. the invention in a position lialiway'between the dead centres of the pistons,

Fig. l presenting a view at right angles to the engine sha-ft partly in section and Fig. 8 an axial section through the arrangement along the line d-tin Fig. 'il' Fis. 9- shows still another variant of the idea or the invention. which is principally applicable to. a, construction of the: wobbler plate diiering from that shown. in Fig. 1.

Fig. i() isa diagrammatic view of the wobbler plate' bodyAv used. in Fig. .9k it the same is seenr in the direction: of theV arrow A in Fig. 9, i'. e. in the 3 direction of the tilted crank pin of the engine shaft.

Fig. 11 shows an analogous coupling element as shown in Figs. 3 to 5, but altered in construction to suit the variation according to Fig. 9.

In Fig. 1 the centre line of the engine shaft II is represented by I. The engine shaft I I differs from an ordinary crank: shaft in that it is provided with a tilted crank pin 22 on which the so-called wobbler plate body is so journalled that it is rotatable on the crank pin 22 but not slidable on it in an axial direction. The centre line 2 of the tilted crank pin intersects the centre line I of the engine shaft at an angle a at a point O, which point is also called the wobbler plate centre or wobbler plate plane centre as the plane situated in the point O at right angles to the tilted crank pin 22 or the centre line 2 thereof is called the wobbler plate plane.

When the engine shaft II is rotated the wobbler plate plane performs, as is well known, its characteristic wobbling motion. In order that the wobbler plate mechanism can function at all it is necessary to prevent the wobbler plate or the wobbler plate body 3 from participating in the rotation of the engine shaft II by means of some suitable anchoringr arrangement. Such an arrangement has not been drawn in the figures partly because it constitutes a separate problem and is therefore not the object of this invention and partly to permit a clearer illustration of the idea of the invention. Such anchoring means are described, for instance in my copending applications Serial No. '715,265 filed December 10, 1946, now Patent 2,550,613, and Serial No. 42,116 led August 2, 1948 now Patent 2,550,612. It may, however, be mentioned, that as` is well known, the condition for the dynamic counterbalancing of the mass forces of a wobbler plate engine is that all of the points situated in the wobbler plate plane and at a distance R from the wobbler plate centre O describe three-dimensional paths resembling lemniscate motions which are in all respects equal to one another and which are situated on a spherical surface with the radius R. The greatest length S of these loop curves corresponding to the distance between the dead centres of the mechanism or its length of stroke is the equal to 2.R.cos a and their greatest widths d in a tangential direction d=R.(l-cos a). In the middle of Fig. 1 such a movement path has been drawn in as a dash and dot line L around the point O.

The wobbler plate body 3 has only been dlagrammatically indicated in the figures and has therefore here, as an example, been given the fundamental form of a double truncated cone with a common base situated in the wobbler plate plane. The wobbler plate body can, of course, be formed in another manner and is independent of the present invention. Some designers prefer, for instance, to give the wobbler plate body the form of a single cone which, in the centre of its base situated in the wobbler plate plane, is journaled on universal joints, and the engine shaft does not pass through the Wobblei` plate body but is coni-ined to a single crank arm in which the cone shaped point of the -wobbler plate body is rotatably journaled, and 4by means of its crank arm the engine shaft forces the cone shaped point of the wobbler plate body to move in a circular path. Furthermore a number of other constructional forms of wobbler plate bodies of so-called wobbler plate rings are 4 known, which can also be utilized with the present invention.

The working cylinders of all wobbler plate engines are, as is well known, arranged around the engine shaft II approximately as cartridges in a revolver drum. For the full realisation of the numerous principal advantages of the woblbier plate system in the most suitable manner it is expedient to arrange the cylinders on both sides of the wobbler plate plane, so that two working cylinders always lie in coaxial alignment with each other. For the sake of clearness only four such cylinder' pairs, providing eight working cylinders have been assumed in Fig. 1, and of these only two have been diagrammatically indicated in the axial section, namely 5 and 5I). Likewise, eight cylinders are assumed in the case of the embodiment of Fig. 1A, two cylinders, 5 and 6G, being shown. Normally in practice however, a larger number of cylinders will be arranged, partly to achieve the maximum possible engine output with the minimum space and constructional weight, partly to obtain as even a torsional moment as possible.

In this construction example as many journal pins 4 as there are pairs of cylinders are secured to the wobbler plate body to extend in radial direction from its periphery. On each of these pins 4, a coupling element 40 is so mounted that its longitudinal axis is always at right angles to the centre line cf the corresponding pin 4, and that it is only rotatable around but not displaceable along the last named line. The pin 4 and the element 4Qfthus constitute a kind of Cardan joint.

The fundamental form of the element 40 is illustrated by the Figs. 3, 4 and 5 in three different projections, and partly in section. As the Figs. 3, 4 and 5 show, the element 40, which is cylindrical on the outside, is provided with a hole 4I in a direction at right angles to the axis of the element 48. This hole 4| serves as a rotatable bearing for the element 43 on the pin 4. Displacement along pin 4 is prevented by the end surface 43 of the pin restingagainst a wall 44 at the bottom of the hole 4I, while, for example, a nut 45 is threaded on an extension bolt projecting from the pin 4 and retains element 4B on pin 4. Y

The big-end of piston rod 5I is mounted not only rotatably but at the same time axially slidably on the element 4G, i. e. laterally slidable relative to the center of the Cardan joint formed by the pinrli 'and the elementllil.

This` possibility of lateral sliding of the piston rod along the one of the elements 4Q secures for this Cardan joint three degrees of freedom, which is one of the characteristics of the invention rela#- tive to the known art. This lateral slideability in thecoupling of the piston rods to the wobbler plate permits a radius in the wobbler plate plane through the centre of the coupling element i. e. the center of the pin 4 and the element 4U to freely describe the apparent oscillating movements around the centre line of the engine shaft, which are characteristic for the theoretically correct motion of the wobbler plate. The small end of the piston rod 5I is in a manner known per se rotatably journaled on a gudgeon lpin 54 inthe piston 52. v

According to the construction illustrated in Fig. l the second piston 55 of the piston pair is attached by means of a so-called articulated connecting rod 53 which is in a known manner rotatably journalled both relative to the piston 55 by means ci' the gudgeon pin 5c and relative: to the main piston rod :t by means. of bearingbolt, 153 carried by the bearing; brackets 55 on the big-end of the main piston rod. The bearing bolt 5;'5 is arev ranged parallel to the axis of but laterallyoffset in relation to. the elementv all: so that the two. con meeting rodsll and 53 of the piston lea-ir 52;, 55 constitute a knee action unit which, on the other hand', is rigid'lin a direction at right: angles to the planey of bending, i. e. rigid in a direction tan gential to. the Wobbler plate. This. is indicated i11- ter alla, by the piston pai-r drawn in the centre of Fig. l andgby the design or' the `piston rods 5i! and 53. The big-end of the. main piston rod' A5I provided with openings Sil: which allow suilcient freedom of movement between the pin :t and its extension bolt, if any. on the. one side and the piston. rod 5l, on the. other side, rotatably and slidealoly mounted on the element to.

A Variant` construction is. shown in Fie. la differs trom the one; rst described, appearing on. the left. hand.- side of Fig; l in that the .piston rod. 63 or the' lower piston S5 isx in a. manner known per se formed as. a forked piston4 rod which is rotatably iournaled on and encompasses the outside of the big-vend of 'the piston rod, Si... In, this way the axis of; rotation of` the Piston rodi $3 'coincides with the axis ci rotation of' the piston rod 6l both axes. passing through the center point perneldicularly to the plane, of

Fis. 1

Fig., a shows the ioining together of the bigendsoi the two piston rodsv 6l; and. G3i partlyin the left halt of the. sure in a section on they line I-- in. Fig... LA. partly'. in the right half' ci the. Fig. 2.,. a viewer the saure detail ii it is; seenv in a, direction atv iight. angles to the .engine sliait Il. The element, 4o can. eten in this variant. be suitably termed in the. same, manner as shown by FissA 3, 4 and o.

Figs. 6, 7 anjd 8 show an additional variant of the idea of; the invention. Fig. 6. a, View of a pair of pistons'in a. direction. tangential to the wobbler plate, where the, mechanism is shown, in an axial section. through the. nin 4.., Fics. '2 and 8. show the same arrangement when the pistons are in, a position between. the dead centres and seen from twodiierent directions at right angles to one another... The piston l2Y has been drawn as a sectionthroosh the. audgeon pin and the cylinder axis ,in order to illustrate an expedient detail construction for theY attachment .of .the piston to the. small end or the. piston rod. Fiera an axial section through the mechanism, show# ing the upper piston rod on the. section .line 84H8 in Fig. 1' and a. side. view-zot the lower piston rod 13.

As is made evident by theI three last. named iig--` ures the two. piston rods?! and 13 are identical and rotatably connected to a link member havingra central, bearing sleeve 80 byV means oi crank pins i8 and 1S haring parallel axes which are later allyy offset on both sides of and perpendicular to the axis of the. pin- 4.. This central bearing sleeve. 80 is not rotatably mountedon the element. 40 and is only longitudinally slidable therevon, i. e. according to the-idea of' the invention, in a direction at right angles to the pin 4. This axial siideablt'y of the bearing sleeve B0 without rotation relative to the pin 4D is assured, for example in FgQ, in that the outer-opening 59 in the bearing sleeve 8l! is oval andthe width ,of

the oval is equivalent to the outer diameter-"of a bearing ring 48 which is rotatably journaled on a. hearingL blush 41 which. last named slid on toy an extension or the pin 4 and held on the same. by .means of a vthreaded nut. "4'5.. In this way the element, 40 is yat the. same time. located on the pin 4 in the axial direction duc to. the bearing bush 41.' restingzin the bottom of the hole 4I in the. element 40., and the wall 44 in its turn ind's support. against the end surface of thel pin 4 see also `Figs. 3 to 5.). The nut 45 only tightened so much that the Wall 4'4 and the end surface -43 of .the pin 4 can function as an axial bearing. The length of the oval outer opening 53 in the central bearing sleeve 80 lies in the axial direction of said sleeve and must be at least equal to the sum of the diameter of 'the bearing ring plus the Width d of the lem-niscate shapedmovementl path L V(see Fig. 1) Which'the cen-trepoint. describes during an engine revolution.

Fig-si '7 and 8 also illustrate a means foi-"preventing the pistons from binding in the 'cylinders if their vlongitudinal axes should not coincide accurately, or the rotary axes of al1- y'of the piston rods in the knee action unitshould not lie exactly parallel to one another or to vthe axis of the bearing sleeve SS. The means consists therein that the small ends of the piston rod-s are connected to the piston by vmeans of universal joints, for example as suggested in Figs. 7 and 8. Instead of the cylindrical holeat the small ends of the piston rods, a ball race is arranged in which a rin-g el spherical on its outside is fitted. The ball race in the small end of the piston rod is provided on its one side with cylindrical milled out recesses which are as wide as the ring 8i is thick. The ring 8l can therefore be slid into the ball race from that `side and their be rotated The piston rod can be lat erally located on the gudgeonup'in 'M by inserting distance rings 32 between the flat faces of the spherical ring and the inner wall ofthe piston. y

It may here be interjected that unnecessary lateral playr between the pistons and their piss ton rods should be avoided in all the constructional forms, partly to avoid disturbing scccndary noise during the running of the engine, partly to provide against unsymrnetrical and aclverse loads on the knee action unit slideably mounted on element 4B. Purely theoretically it is true that itshould be possible to assign the Whole of the lateral slideability of the knee aeticn unit to the gudg'eon pins, but this Should in practice be accompanied by considerable draw* backs because the load on the gudgeon pins is continually fiuctuatingand is, at the same inf starrt, very different on the two gudgeon pins of two cooperating piston-s. lAs a result, even the friction between the small ends ct thefpistcn rods and their respective gudgeon-pins is unsymmetrical in comparison with the connecting mechanism and this should occasion adverse` wor-king conditions for the various bearing surfaces of the Whole piston connecting mechanism.

It is true that the lateral pressure ofthe pistons against the cylinder' walls will, in thel case of' the constructions accor-ding' to Figs. 6, 7 and 8, be somewhat greater than in the ease of the other Variations shown in the drawings,l but it amounts nevertheless at .its maximum at the intermediate position ci" the pistons between their dead centres only to about half the values reached in ordinary crankshaft engines. An ad'- vantage of this construction compared Withvthe other constructions is, on the other hand, that the stroke of the pistons and hence the cylin der capacity is about greater for the same angle a of inclination of the tilted crank pin and for the same distance between the cylinders and the engine shaft.

Fig. 9 shows a further construction which is particularly suitable if the designer wants to form the whole wobbler plate body of light metal. The pins 4 are not here, as in the earlier examples, arranged in a radial but in a tangential or peripheral direction to the wobbler plate and with their centre lines in the wobbler plate plane. The element 4I) is rotatable around pin 4 but not slidable on same as this is prevented by the fitted distance tubes 41. In other respects the construction compares most closely with that illustrated in Fig. l with the exception of that, in this variant, the hole M in the elementy passes right therethrough, which is apparent from Fig. 1l. The bolts in the knee action unit are, of course, again parallel to one another but are at right angles to the pin 4. The knee action unit is here axially slidable along the element 40, that is, in a radial direction relative to the wobbler plate body, i. e. in a direction at right angles to the pin 4.

Fig. l0 shows a portion of the wobbler plate body used in Fig. 9 and seen in the direction of the tilted crank pin and of the arrow A in Fig. 9. Here, as previously, only four pairs of cylinders have been assumed for the sake of clearness of .j

the gures although, as mentioned, in practice it is more advantageous togroup a larger number of cylinder pairs around each wobbler plate.

It is true that the piston attachment mechanism according to the present invention is, from the kinematic pint of view, not absolutely correct, but as the deviation from the absolute correct values is, even in the most adverse case, less than 0.25%, this circumstance has no practical importance whatever.

However, the many practical advantages which the present invention affords in comparison with the numerous hitherto known designs are of all the more positive value. Of these may be named, for instance, that the lateral pressure of the pistons against the cylinder walls is reduced to a minimum, that the piston rods are not subjected to bending loads or fatigue risks, that all the vital parts can be constructed and dimensioned in accordance with the requirements and experience regarding strength and service reliability and especially for high compression and high speed internal combustion' engines. If the design is applied to two-stroke engines. being particularly suitable. the resulting loads on the connecting joints, the wobbler plate body, the engine shaft and on all of the bearing surfaces will always only amount to the difference between the Working pressure on one piston reduced by the mass forces of the two pistons and of the knee action unit of the piston rods. The design is composed of only simple elements well proved in practice, is inexpensive to manufacture and assemble, permits ample dimensioning of all bearing surfaces and material cross-sections, and obviates the risk of the pistons or other parts binding or seizing on account of running loads or deformation at various conditions of heat. vThe reciprocating piston movement is combined with a simultaneous slight rotary movement around the cylinder axis since the apparent oscillations of the wobbler plate body around the engine shaft are transmitted to the pistons through the connecting mechanism. This prevents scores arising in the wearing surfaces of the piston and the cylinder, distributes the lubricating oil film more evenly, etc. The same favorable type of movement, i. e. a combination of rotary and reciprocating movement, occurs in the constructions according to Figs. 1 and 9 between the element 40 and the big-ends of the main piston rods '5l and =6I.

The idea of the invention permits, of course, further variations and combinations, and is applicable to other constructions of wobbler plates or wobbler plate mechanisms, and to motive power engines as well as workingv engines, such as compressors, pumps, etc. which make use of the wobbler plate principle.

I claim:

1. In Ia piston engine of the wobbler type, the combination, with a .main shaft, a rigid nonrotatable wobbler body non-displaceably journaled thereon, at least two pairs of cylinders having their axes parallel with the axis of rotation of said shaft and with the cylinders of each pair located on opposite sides of said wobbler body respectively and coaxial with each other, pistons reciprocable on opposed Working strokes in each pair of cylinders `and means comprising articulated piston rods connecting each pair of pistons, of a knee action coupling unit for connecting the piston rods of each pair of pistons to said wobbler body, each of said units being bendable only in a first plane including the common axis of the pair of cylinders and comprising a coupling element turnably mounted on said wobbler body at a fixed radius from the center thereof to turn relative to the wobbler body about an axis extending inthe plane of the wobbler body, and the piston rods of the pair connected' to said coupling element being connected so as to turn only in said rst plane and to slide relatively to said element in a direction perpendicular to said rst plane.

2. An engine as defined in claim l, -in which said iirst plane extends radially from the axis of rotation of said main shaft.

3. An engine as dened in claim 2, in which said axis about which said coupling element turns extends radially .in the plane of the wobbler body from the center thereof.

4. An engine as dened in claim 1, in which said iiist plane extends peripherally with respect to said wobbler body.

5. An engine .as dened in claim 4, in which said axis about which said coupling element turns extends in a peripheral direction in the plane of the wobbler body.

' 6. An engine as defined in claim 1, in which said coupling element is connected to the wobbler body by a pivot connection preventing displacenient of the coupling element relative to the wobbler body.

i '7. An engine as defined in claim 1, in which a first piston rod -in each pair is mounted to have both turning and displacement movement relative to the coupling element and the second piston rod of the pair is non-displaceably pivoted on said first piston rod. to turn in said first plane.

8. An engine as defined in claim 7, in which said second piston rod is turnable about an axis coinciding with the axis about which said rst piston rod turns.

9. An engine as defined in claim 8, in which said piston rods-are provided with sleeve-shaped end portions, the sleeve-shaped portion of said first piston rod encircling said coupling element and the sleeve-shaped por-tion of said second pis- 9 ton rod being coaxial with `and encircling the sleeve-shaped portion of said first piston rod.

10. An engine as dened in claim 7, in which said second piston rod is mounted to turn about an axis parallel with and laterally oiset from the axis `about which said rst piston rod is turnable.

1l. An engine as deiined in claim l, in which the coupling unit includes a link member axially displaceably and non-rotatably mounted on said coupling element, the piston rods of the associated pair being individually connected to said link member to be non-displaceable with respect thereto and turnable about axes each oiset with respect to and perpendicular to the axis about which said coupling element is turnable with respect to said wobbler body.

l2. An engine as dened in claim 1, in which a universal joint connection is provided between each of said piston rods and the piston to which it is connected.

13. In a piston engine of the Wobbler type, the combination, with a main shaft, a rigid nonrotatable Wobbler body non-displaceably journaled thereon, yat least two pairs of cylinders having their axes parallel with the axis of rotation of said shaft and with the cylinders of each pair located on opposite sides of said wobbler body respectively and coaxial with each other.

10 pistons reciprocable on opposed Working strokes in each pair of cylinders and means comprising articulated piston rods connecting each pair of pistons, of a motion transmitting unit connecting the piston rods of each pair to said Wobbler body, each such unit comprising a coupling element, means including said element providing a Cardan type joint between said Wobbler body and said pair of rods, said element being turnably mounted on said wobbler body at a xed radius from the center thereof land providing a journal and the connection between said rods and said element providing for both turning movement of the rods relative to the axis of the journal and movement of the rods axially with respect to the journal.

EDMUND ERNST KARL SPARMANN.

References Cited n the le of this patent UNITED STATES PATENTS Number Name Date 1,787,493 Redrup Jan. 6, 1931 1,814,946 McGeorge July 14, 1931 2,247,527 Stinnes July 1, 1941 FOREIGN PATENTS Number Country Date 212,884 Great Britain May 18, 1925

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