TECHNICAL FIELD

The present invention relates to a machine of the kind set forth in the preamble of claim 1.

BACKGROUND ART

In previously known machine ^' s of this kind, the means trans¬ mitting the reciprocating motion from the wobble rotor to the pistons have either comprised a number of individual slide pads, one for each piston, cooperating slidingly wit the inclined bearing surface on the wobble rotor, or a sin¬ gle wobble plate cooperating with the wobble rotor through a combined radial and thrust bearing and transmitting the motion to the individual pistons through linkages or other complicated mechanisms. Naturally, such individual slide pads or such motion-transmitting linkages have represen¬ ted a substantial part of the manufacturing costs for the machine, for which reason it would be desirable to find other and less costly ways of transmitting the recipro¬ cating motion to the individual pistons in their cylin- ders.

DISCLOSURE OF THE INVENTION

It is the object of the invention to provide a machine of the kind referred to initially, in which the mechanism transmitting the reciprocating motion from the wobble ro- tor to the individual pistons is considerably simplified in comparison to the previously known machines referred to above, and this object is attained by a machine, ac¬ cording to the present invention characterized by the fea-

tures set forth in the characterizing clause of claim 1. With this arrangement, the individual slide pads referred to above are replaced by a single member, i.e. the wobble plate, which is held in place solely by the pistons coo- perating with the recess or recesses in the wobble plate.

Advantageously embodiments of the machine according to the present invention are described in claim 2-5, and the no¬ vel technical effects thereby attained are explained in the following detailed portion of the present specification.

BRIEF DESCRIPTION OF THE DRAWING

In the following detailed specification the invention is explained in a more detailed manner with reference to the single Figure of the drawing, which shows the parts of the machine relevant to the present invention in axial section.

DESCRIPTION OF THE PREFERRED EMBODIMENT The exemplary embodimen-t of a machine according to the invention in the form of a high-pressure liquid pump, of which only the components directly relevant to the pre- sent invention are shown in the drawing, comprises a number of stationary cylinders 1 with their longitu¬ dinal axes 2 parallel to the axis 3 of a drive shaft 4, through which mechanical energy is supplied to the pump by means not shown, such as a suitable motor (it should be noted that the axes 2 of the cylinders 1 may also form acute angles with the shaft axis 3), in each cylinder 1 a plunger piston 5 slidable in the cylinder and having a free end 6 projecting from the cylinder and abutting against a wobble plate 7, that is common to all the pistons and is rotatably suppor¬ ted against a wobble rotor 8 secured to the drive shaft 4 and ha¬ ving an inclined bearing surface 9 cooperating with

the wobble plate 8, a housing 10, in which the cylinders 1 are secured in a manner not shown, - a conical roller bearing 11,12,13 inserted between the housing 10 and the wobble rotor 8 and with its roller races 11 and 12 converging away from the wobble plate 7, i.e. towards the left on the drawing, the bearing comprising rollers 13 rolling between the races 11 and 12, as well as suitable means, such as a roller cage, for guiding the rollers in their operating tracks, and finally a plane roller bearing 14,15,16 inserted between the wobble plate 7 and the wobble rotor 8 and having plane roller races 14 and 15 on the wobble plate 7 and the wobble rotor 8 respectively, this bearing comprising cylindrical rollers 16 as well as suitable means, such as a roller cage, for guiding the rollers in their o- perating tracks.

The pistons 5 are held in permanent contact with the wob- ble plate 7 by suitable means, such as return springs (not shown) urging each piston towards the wobble plate 7, i.e. towards the left in the drawing. The rounded free ends 6 on the pistons 5 are thus kept in constant engagement with a shallow groove 17 formed on the side of the wobble pla- te 7 opposite the roller race 14. The groove 17 is prefe¬ rably of part-circular cross-sectional shape as seen in meridian section, and extends all the way around the wob¬ ble plate 7, the latter here in fact being a ring with a central opening 18 accommodating a nut 19 holding the wob- ble rotor 8 secured on the drive shaft 4.

The radius of curvature 20 of the groove 17 is somewhat larger than the radius of curvature 21 of the cooperating free ends 6 on the pistons 5, thus allowing for a certain relative radial movement between each piston 5 and the

the wobble plate 7 as the latter wobbles about the axis 3 of the drive shaft 4 whilst being driven to do so by the rotating wobble rotor 8. In this connection it should be borne in mind that neither the end apex points 22 on the pistons 5 nor their tangency points 23 will lie on a per¬ fect circle, due to the axis 24 of the wobble plate 7 for¬ ming an angle 25 with the axis 3 of the drive shaft 4.

Due to the permanent engagement between the free ends 6 on the pistons 5 and the shallow groove 17 in the wobble plate 7, no further means are required to keep the latter in place in its operating position shown. Because of the variations in the reaction forces from the various pi¬ stons 5 caused by the cyclic and non-cyclic pressure va¬ riations within the individual cylinders 1, the wobble plate 7 may not always be urged to take up the position indicated on the drawing, in which the two tangency points 23 shown lie on a common straight line at right angles to the axis 24 of the wobble plate 7, but may take up - or rather move through - positions deviating slightly from this position in directions parallel to the planes of the roller races 14 and 15 and angularly with respect to the axis 24. Due to the difference between the radii of cur¬ vature 20 and 21, such slight deviations may occur with¬ out risk of damage to the cooperating parts.

It is possible to use a conical thrust bearing instead of the plane bearing 14,15,16 with cylindrical rollers 16, but in that case the wobble plate 7 would lose two de¬ grees of freedom in the above-mentioned deviations, i.e. in two mutually perpendicular directions parallel to the planes of the roller races 14 and 15, only the freedom of relative rotation remaining. For this reason the arrange- ment shown with a plane roller bearing is preferred, even if the contact between the rollers and the races is not pure rolling as in conical bearings with co-apical rol-

lers and races; the slight rubbing has, however, not cau¬ sed any problems in practical embodiments.

It is also possible to use individual recesses in the wob¬ ble plate 7 for each piston 5 instead of the common groove 17 shown, but such an arrangement could cause the piston ends 6 to run up against one side of the recesses and re¬ main there, due to the cyclically varying reaction forces from the pistons doing their pumping work in their indivi¬ dual cylinders. This would, of course, cause undue wear on the recess sides referred to, for which reason the ar¬ rangement shown with a continuous groove is preferred, al¬ lowing the wobble plate to rotate slowly by a kind of "craw ling" action, so that the wear is evenly distributed on a considerably larger surface area than if individual re- cesses were used. The arrangement with a continuous groove also makes the wobble plate 7 simpler to manufacture, as the continuous groove may be formed in a single turning operation, whereas individual recesses would require at least one machining operation for each recess.