The present invention relates to a connecting rod for a re¬ ciprocating machine, in particular a compressor for refriger¬ ating equipment. '

In more detail, such a connecting rod comprises: - a first main piece which includes a connecting rod small end, a shaft which extends longitudinally and a half- big end which defines a semi-cylindrical concave surface, - a second main piece constituted by a cap having a semi-cylindrical concave surface, the semi-cylindrical con¬ cave surfaces of the first main piece and the second main piece having respective pairs of mating ends, and - securing means for securing at least one of the pairs of mating ends' in such a manner as to form the connecting rod big end defining on its inside a cylindrical eye, in a dia¬ metral plane of which the pairs of mating ends are located.

A known connecting rod of that type is described in the docu¬ ment EP-A-O 787 910, in which various embodiments of the above-mentioned mating ends, for example with a dovetail joint, are illustrated.

However, that type of joint causes deformation of the con¬ tacting portions which may bring about a deviation from the complete circularity of the profile of the eye of the con¬ necting rod big end, which deviation, even if slight, may compromise the functionality of the reciprocating machine.

In addition, the joints according to the prior art lead to the production of rigid structures which are not capable of adaptation to the shape of other pieces on which the connect¬ ing rod is typically assembled, in particular the crank pin.

In order to remedy those disadvantages, the present invention relates to a connecting rod which has the features indicated at the beginning of the present description and which is characterized in that, in each of the.pairs of mating ends, a first end has an appe.ndage which protrudes outwardly from the connecting rod big end and defines on its inside a cavity in which a projection protruding from a second end is accommo¬ dated, the coupling between the appendage and the projection being produced with interference in the direction identified by the shaft and with clearance in the direction perpendicu¬ lar to that identified by the shaft and lying in the general plane of the eye.

According to the invention, the coupled portions of the mat¬ ing ends are located externally with respect to the eye of the connecting rod big end, so that any deformation caused by the coupling does not compromise the circularity thereof.

In addition, the fact that the coupling between the mating ends is produced with interference in the direction identi¬ fied by the shaft enables the two main pieces to remain join¬ ed even in the absence of the securing means. At the same time, the fact that the coupling between the mating ends is produced with clearance in the direction perpendicular to that identified by the shaft permits automatic alignment of the eye of the connecting rod big end with the crank pin.

Further advantages and features of the present invention will become clear from the following detailed description which is given by way of non-limiting example with reference to the appended drawings, in which: Figure 1 is a perspective view of a connecting rod ac¬ cording to the invention, Figure 2 is an exploded perspective view of the connect¬ ing rod of the previous Figure, Figure 3 is a side view of the connecting rod of the previous Figures, Figure 4 is a front view of the connecting rod of the previous Figures, and Figure 5 is a view of a detail of the connecting rod of Figure 4 on an enlarged scale.

A connecting rod for a reciprocating machine, in particular a compressor for refrigerating equipment, comprises a first main piece 10 and a second main piece 12, which are advanta¬ geously producible in sintered metal or reinforced plastics material, for example polyphenylene sulphide (PPS) incorpo¬ rating glass fibres.

The first main piece 10 includes a connecting rod small end 14, a shaft 16 which extends longitudinally and a half-big end 18 which defines a semi-cylindrical concave surface 20, while the second main piece 12 is constituted by a cap having a semi-cylindrical concave surface 20. Advantageously, the ratio of the height to the width of the shaft 16 is from 1:1.6 to 1:2, so that the shaft has some flexibility, which makes it possible to make up for any errors in perpendicular¬ ity between the cylinder and the driving shaft.

The semi-cylindrical concave surfaces 20 of the first main piece 10 and the second main piece 12 have respective pairs constituted by first and second mating ends 22, 24 so as to form the connecting rod big end which defines on its inside a cylindrical eye, in a diametral plane of which the pairs of mating ends 22, 24 are located.

Each first end 22 has an appendage 26 which is shaped in the form of a C in the general plane of the eye and which has a central portion 28, from whose ends extend respective trans¬ verse branches 30 on whose .lateral surfaces respective grooves 32 are formed. Each appendage 26 protrudes outwardly from the connecting rod big end and defines on its inside a cavity 34 in which a projection 36 which protrudes from the second end 24 is accommodated. The coupling between each pair formed by an appendage 26 and a projection 36 is produced with interference in the direction identified by the shaft 16 and with slight .clearance (for example of the order of a few hundredths of a mm) in the direction perpendicular to that identified by the shaft 16 and lying in the ' general plane of the eye (see arrow 37) .

This interference enables the two main pieces 10, 12 to be kept assembled under static conditions but is not capable of ensuring the strength of the connection during the operation of the reciprocating machine of which the connecting rod forms part. This result is achieved owing to the presence of means for securing at least one of the pairs of mating ends 22, 24. The securing means are produced in the form of a U- shaped clip 38 having a base portion 40 from whose ends ex¬ tend respective wings 42 which can be opened out resiliently and which are recessed along the external surface and have at the distal end a respective inwardly projecting tooth 44. A projection acting as a spacer 46 also protrudes inwardly from the base portion 40 of the clip 38.

The installation of the clip 38 is effected by fitting the wings 42 in the grooves 32 formed on the lateral surfaces of the transverse branches 30 of the respective appendage 26 and by opening them out resilientIy in such a manner that the end teeth 44 of the wings 42 engage beyond the end surface of the transverse branch 30 opposite the branch facing the base por¬ tion 40 of the clip 38.

In the connecting rod just described, the coupled appendage 26 and projection 36 of each pair of ends 22, 24 are located radially on the outside with respect to the eye of the con¬ necting rod big end, the circularity of which is thus not compromised by the deformation occurring as a result of the coupling.

In addition, the clearance permitted by that coupling in the direction 37 perpendicular to that identified by the shaft 16 permits automatic alignment of the eye of the connecting rod big end with the crank pin, preventing jamming and similar difficulties.

Naturally, the principle of the invention remaining the same, the details of construction and forms of embodiment may be varied widely with respect to those described purely by way of example, without thereby departing from the scope thereof. In particular, the appendages 26 with the respective cavities 34 could be carried by the second main piece 12 and, corre¬ spondingly, the projections 36 accommodated in those cavities 34 could be carried by the first main piece 10.