US2282722A - Crosshead mechanism - Google Patents

Description

May 12, 1942- E.I s. HALL 2,282,722

c RossHEAD MEcHANIsIM Filed dan. :50, '1940 Patented May 12, 1942 UNITED STATES PATENT OFFICE CROSSHEAD MECHANISM Edwin s. Hau, New Haven', Caml. Application YJanuary 30, 1940, Serial No. 316,402

(o1. 12s-5s) 6 Claims.

lowers, while the swashplate has plane working faces which may coact with slippers seated in the piston members. A wabbler does not rotate relative to the cylinders, being mounted on bearings on and inclined to the shaft. 'This invention is applicable to Vcrank type, cylindrical cam, and swashplate mechanisms, but it is especially advantageous with the wabbler mechanism and may conveniently be described as applied thereto, it being understoodthat any of the other mechanisms may be used if desired. The salient object of the invention is to provide a crosshead type of piston mechanism of simple, compact, and light-weight construction.

With double-ended pistons, itis desirable that their central portions function as crossheads on which to carry the lateral loading which, with the better mechanisms, comprises the torque reaction of the engine. When the central portion of the piston member serves as a crosshead, the member is not subject to beam loading, and the pistons are free to perform 'their primary function as ring carriers, without cocking or slap, and with less friction loss. In an engine having two sets of cylinders with the reciprocatingrotary mechanism between them, it `has been common practice to split the engine .on a plane either longitudinal or transverse relative to the cylinders. The longitudinal split is undesirable because of lack of symmetry of the major parts. The transverse split has the advantage of axial symmetry, but care must be used that the opposed cylinders be exactly coaxial for .the proper operation of the common piston member :therein. It would obviously be more desirable if the piston member, especially when it has a ycentral crosshead, could operate in a single unbroken cylinder. An object of this invention is to provide, in an engine or pump mechanism split transversely and having double-ended pistons of the crosshead type, cylinder sleeves extending from one end of piston travel to the other, -the central portions of the sleeves yserving as crosshead guides. Further objects are to use the cylindersleeves as means for fastening the casing members or cylinder blocks together, vand to provide an Vapproved wet liner `cylinder construction, the sleeves serving this purpose as well as that of crosshead guides.

Further objects are to provide a'wabbler mechanismA of the `type in lwhich substantially no torque reaction is carried by the wabbler, the wabbler serving to distribute the torque reaction vamong the several piston members as lateral loading upon their respective crosshead surfaces, this-useful loading being lsubstantially the only lateral( loading 4upon them; and to provide adequate wristpin bearing area in a piston member capable of passing straight thru the cylinder sleeve, the sleeve extending continuously from one .end of piston travel to the other.

These and other objects of the invention Awill be clear from the following description in connection with the drawing in which Fig. 1 is a longitudinal :section of van engine or pump mechanism;

Fig. 2 is a' transverse Lsection on the mid-plane of -the mechanism and on the mid-plane of the wabbler; and

Fig. 3 is 'a radial view, kpartly insection, of the piston member of Fig. 1 and :associated parts.

Referring to the drawing, shaft VIII is mounted on bearings II in cylinder Yblocks I2. Wabb-ler I5 is mounted on bearings-'I6 whose'inner races are clamped between boss members I1 with spacer sleeve 23 between them. Boss members I'I are fixed on shaft `ID in any suitable way. Wabbler I5 is provided with a series of longitudinal ball `races' '3l; 'corresponding ball races 3| are formed longitudinally in vmembers 32 fixed to cylinder blocks I2. One of the balls 33 is operable in each pair of races 30 and 3I. In this manner wabbler I5 is prevented from rotating relative to cylinder blocks I2 while shaft I Il and boss members I'I can Vrotate in bearings IIA imparting the characteristic wabbling motion to wabbler I5.

Wabbler I5 has arms 25, one for each piston member I4. Each arm 25 has a cylindrical bore with its axis tangent to a circle inthe plane of wabbler I5, lthe bore being rotatable and slidable on wristpin 25 which is fixed in radial -crosshead or wristpin carrier 2`I by setscrews 28. Wristpin carrier 2-I is rotatable and slidable in bore 29 in piston member I4, the axis of bore 29 bein radial to shaft I0.

`Piston members I4' are' reciprocablegi-n cylinder sleeves I3, each sleeve I3 extending from the cylinder head of one block I2 to that of the other block I2 and forming a wet liner in both cylinder blocks I2. The central portion of cylinder sleeve I3 is provided With symmetrical openings 2|] one for inspection purposes and the other to accommodate the movement of wabbler arm 25; on either side of openings 20 the walls of sleeve I3 serve as crosshead guides for .piston member- I4. The piston member I4 may pass straight thru sleeve I3, and its central portion serves as a crosshead 34 in sleeve I3, the skirts of the pistons being of smaller diameter so, as to reduce oil shear area and to avoid beam loading on the piston member I4, the lateral loading on piston member I4, comprising vits share of the engine torque reaction, being carried on crosshead 34. The central portion of sleeve I3 is thickened to carry packing rings 2I of any suitable material to seal the coolant in jackets 42 and to make up in strength for the material removed by openings 20. The ends of sleeve I3 are also thickened to withstand the higher gas pressures and to provide for the att'achment of studs I8, preferably screwed into the thickened ends of sleeve I3, and spaced evenly about the ends of sleeve I3 in ample number to carry the tension loads imposed upon sleeve I3 by gas pressures acting on the piston and cylinder heads. Suitable packing is used in grooves 22 of cylinder blocks I2 which receive the ends of cylinder sleeves I3, to insure that the joint be tight against leakage of gas from within the cylinder or coolant from the jacket space 42. Studs I8 may be furnished with nuts I9.

It is desirable that a continuous oil passage be provided from within shaft I0, or from within boss members II, to the crosshead surfaces 34 of piston members I4 thru wabbler arms 25 and associated parts. To prevent leakage of excess oil thru ball bearings VII from this oil passage, sealing plates 24 are provided.

In assembly, bearings IB are assembled with wabbler I5, sleeve 23 and plates 24 upon boss members I'I. This assembly is then mounted on shaft I0. Wristpins 26 and carriers 2'I are then assembled on arms 25 and locked by setscrews 28. Piston members I4 are inserted in their several cylinder sleeves I3, and then assembled radially upon their several Wristpin carriers 21, and inserted longitudinally into one of the cylinder blocks I2 with suitable packing and sealing rings 2I in place. Then the other block I2 may be drawn on, and the two blocks fastened together upon sleeves I3 by nuts I9 drawn down on studs I8, after which the wabbler case may be closed by oil pan 35 extending from one cylinder block I2 to the'other.

In operation, rotation of shaft I is accompanied by reciprocation of piston members I4, and the oscillatory combined rotation and axial sliding of wristpin carrier 2'I Within the bore 29 in piston member I4 and of wabbler arm 25 on Wristpin 26. Displacement of the center of arm 25 from the plane of the cylinder axis, as that center follows its lemniscate path, causes a slight oscillatory rotation oi piston member I4 during its reciprocation, tending to improve its lubrication in cylinder I3 and tending also to prevent piston ring sticking.

Rotation of shaft IIJ is also accompanied by the rolling of balls 33 in their races 3U and 3| Balls 33 are maintained with their centers always in the plane which bisects the anglebetween the mid-plane of the wabbler and the plane normal to the shaft thru the center of the wabbler by the interaction of races 30 and 3I. At the position shown at A in Fig. 1, the two races are coplanar, but the ball is positively located by the ends of races 30 and 3| as shown. At all other positions, the ball 33 is positively located at the intersection of the two races 30 and 3|, as indicated diagrammatically at B in Fig. '1.

Most of the proposed wabbler mechanisms have the objectionable characteristic of imposing the engine torque reaction upon the wabbler. For example, when the wabbler is connected to the pistons by ball-jointed connecting rods; it is readily understood that the wabbler `must be lieldagainst rotation in order to turn the shaft at all. (If not so held, the thrust of the rods would merely turn the wabbler on its bearings and tangle up the rods.) In other words, the torque reaction is on the wabbler, and the restraint must be adequate for carrying this heavy load." It is clearly not desirable to load the wabbler restraint so heavily.

The wabbler mechanism shown, having wristpins 26 with their axes tangent to a circle in the plane of theV wabbler, imposes practically no torque reaction on the wabbler. This is apparent from the fact that all Working surfaces of the wabbler are surfaces of revolution about the wabbler axis vortangent to'such surfaces of revolution, so that, essentially, only Vfrictional forces can act to turn thewabbler. The torque reaction is distributed among the several piston members I4, and is carried by their crosshead surfaces 34 sliding Within thek central portions of cylinder sleeves I3. This useful lateral loading constitutes the only side thrust carried by piston members I4, and this is one of the reasons for the high efficiency of this particular wabbler mechanism. While in this mechanism, crosshead portion 34 ofpiston member I4 is kept small enough to pass thru cylinder sleeve I3, nevertheless, the bearing area of Wristpin 26 in wabbler arm 25 is of ample size, being about twice that of wristpin bearing areas in engines of the same bore now'in. production.

With the engine torque reaction distributed among the several piston members and substantially no torque imposed on wabbler I5, the wabbler restraint comprising balls 33 and their races 30 and 3| have only the duty of preventing rotation of wabbler I5 against the frictional drag of bearings I6.` lThis vrestraint comprises a uniform velocity universal joint connecting wabbler I5With cylinder blocks I2.

From the foregoing description, it is evident that the objects of the invention as stated have been attained in a practical manner. While' I have shown a particular embodiment of the invention, and its applicationto the wabbler mechanism, it is obvious that the invention could be adapted to serve with a cylindrical cam mechanism or other types, and it is understood that changes may be made in the structure and in the arrangement of the parts without departing from the spirit and scope of the invention as both said casing members as wet cylinder liners and extending from the cylinder heads of one of said blocks to those of the other, studs in the ends of said cylinder sleeves for securing them in said casing members thereby fastening said casing members together with said sleeves in tension during operation, means for sealing the joints between said cylinder sleeves and said casing'members to prevent leakage of cylinder gases or coolant, piston members each including a pair of pistons and a central crosshead portion larger in diameter than said pistons, the central portion of one of said sleeves serving as a crosshead guide for said crosshead, and mechanism operably connecting said crossheads with said shaft.

2. In mechanism of the class described, a shaft, casing members comprising cylinder blocks, bearings for said shaft in said casing members, cylinder heads associated with said cylinder blocks, cylinder sleevesentering both of said casing members as cylinder liners and extending parallel to said shaft from the cylinder heads of one of said blocks to those of the other, means securing said sleeves in said casing members and fastening said casing members together with said sleeves in tension during operation of said mechanism, piston members operable in said sleeves and each including a pair of pistons and a central crosshead of larger diameter than said pistons, the central portion of one of said sleeves serving as a crosshead guide for said crosshead, and mechanism operably connecting said piston members with said shaft.

3. In a parallel cylinder engine of the class described, a frame comprising two similar parts facing each other, cylinder heads associated With said parts, a shaft, bearings for said shaft in said frame parts, seats formed in said frame parts, cylindrical members mounted in said seats and extending from the cylinder heads of one of said parts to those of the other, piston members operable in said cylindrical members and operably 4. In an engine mechanism, a shaft, casing members comprising cylinder blocks, bearings for said shaft in said casing members, cylinder heads associated with saidv cylinder blocks, cylinder sleeves entering both of said casingmembers as cylinder liners and extending parallel to said shaft from the cylinder heads of one, of said blocks to those of thel other, means securing said sleeves in said casing members and fastening said casing membersV together with said sleeves in tension during operation of said mechanism, piston members each including a pair of pistons and a central crosshead of larger diameter than said pistons,rand mechanism operably vconnecting said piston members with said shaft.

5. In a parallel cylinder engine mechanism of the class described, a shaft, casing members comprising a pair of cylinder blocks, bearings for connected to said shaft, and means securing said said shaft in said casing members, cylinder heads vassociated with said blocks, cylinder sleeves entering .both said casing members as cylinder liners and extending from the cylinderheads of one of said blocks to those of the other, means securing said sleeves in said casing members said means comprising a series of studs in the ends of said sleeves, piston members each including a central crosshead, the central portion of one of said sleeves serving as a crosshead guide for said crosshead, and mechanism operably connecting said crossheads to said shaft, said sleeves being in tension axially whenever gas pressure inter-V acts between the heads of said piston members` .including a piston at each end thereof vand a

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