Two-Parts Telescopic Connecting Rod for Alternative Compressors and Method of Assembling Two-Parts Telescopic Connecting Rod in Alternative Compressors

Abstract

The connecting rod comprises a first portion of the connecting rod to be mounted on the eccentric pin of a crankshaft of the compressor and a second portion of the connecting rod to be articulated in a reciprocating piston within a cylinder. One of the first and second portions of the connecting rod comprises a tubular stem portion that receives, telescopically and loosely, and retains, by radial inward deformation, a portion of the engagement stem of the other portion of the connecting rod, said stem portions being held together, in an axial and rotational alignment condition, before being attached by a fixation mean in a relative axial positioning, which results in a portion of the compression chamber and a respective portion of dead volume in the condition of upper dead point of the piston.

1 . Method of assembling two-parts telescopic connecting rod in alternative compressors, said connecting rod comprising a first portion of the connecting rod to be mounted on the eccentric pin of a crankshaft of the compressor and a second portion of the connecting rod to be articulated in a piston having a top face and to be moved, in alternative movement, within a cylinder having an opened front-end face, to be closed by a confronting face of a valves plate, the method being characterized by the fact that it comprises the steps of:
 (i) providing one of the first and second portions of the connecting rod with a tubular stem portion and provide the other portion of the connecting rod with a engagement stem portion having cross-section with outer contour, smaller than the inner contour of the cross-section of the tubular stem portion;   (ii) engaging, telescopically and loosely, the engagement stem portion in the interior of the tubular stem portion;   (iii) conducting the tubular and engaging stem portions to a predetermined condition of axial and rotational alignment between them and of relative axial and preliminary positioning, defining a connecting rod length greater than that required to provide a desired compression chamber portion and a respective portion of minimal dead volume in the condition of upper dead point of the piston;   (iv) subjecting the tubular stem portion to a shaping operation, to form therein circumferential alignments of radial deformations facing inwardly and seated, with predetermined mechanical interference against the engagement stem portion, retaining the latter to the tubular stem portion in said axial and rotational alignment conditions and relative axial and preliminary positioning therebetween;   (v) being the eccentric pin in the lower dead point condition, with the first portion of the connecting rod mounted thereon and the piston mounted in the second portion of the connecting rod and in the interior of the cylinder, rotate the crankshaft to make the eccentric pin going to the upper dead point condition, seating the piston against a stop provided along the front-end face of the cylinder and compressing, axially and telescopically, the tubular and engagement stem portions until the eccentric pin reach the upper dead point position, providing an adjustment of the relative axial positioning of the tubular and engagement stem portions, to a condition in which the top face of the piston defines, with the confronting face of the valves plate, the desired portion of the compression chamber and the respective portion of dead volume at the upper dead point condition of the eccentric pin; and   (vi) securing, mutually and in definitive manner, by a fixation mean, defined among welding, adhesion and brazing, surface portions of the tubular and engagement stem portions.   
     
     
         2 . Method, according to  claim 1 , characterized by the fact that the mutual and definitive fixation of the surface portions of the tubular and engagement stem portions is carried out after the crankshaft being rotated to return the eccentric pin to the lower dead point condition. 
     
     
         3 . Method, according to  claim 1 , characterized by the fact that the piston is mounted in the second portion of the connecting rod and in the interior of the cylinder, before the step of telescopically engaging, the engagement stem portion in the interior of the tubular stem portion. 
     
     
         4 . Method, according to  claim 1 , characterized by the fact that the piston is mounted in the second portion of the connecting rod, prior to the step of engaging the engagement stem portion in the interior of the tubular stem portion, being this latter and the further step of conducting the tubular and engaging stem portions to a predetermined condition of the axial and rotational alignment and relative axial and preliminary positioning, performed with said stem portions and piston outside of the compressor, wherein the method further comprises the subsequent steps of:
 separate the first portion of the connecting rod of the second portion of the connecting rod;   mounting the second portion of the connecting rod and the piston in the cylinder of the compressor and the first portion of the connecting rod on the eccentric pin of the crankshaft; and   engaging, telescopically and with predefined interference, the engagement stem portion in the interior of the tubular stem portion, maintaining the eccentric pin of the crankshaft in the lower dead point condition, prior to the step of rotating the crankshaft of the compressor to bring the eccentric pin to the upper dead point condition, seating the piston against the stop and the step of fixing, mutually and in definitive manner, the portions of the surface of the tubular and engagement stem portions.   
     
     
         5 . Method, according to  claim 1 , characterized by the fact that the step of engaging the engagement stem portion in the interior of the tubular stem portion and the further step of conducting the tubular and engagement stem portions to a predetermined condition of the axial and rotational alignment and relative axial and preliminary positioning, being performed with said stem portions outside of the compressor, wherein the method further comprises, after the step of shaping the tubular stem portion:
 mounting the first and second portion of the connecting rod on the eccentric pin and into the cylinder of the compressor, respectively, with the eccentric pin held in the lower dead point condition; and   attaching the piston, already inserted in the cylinder, in the second portion of the connecting rod prior to the step of rotating the crankshaft of the compressor to bring the eccentric pin to the upper dead point condition, seating the piston against the stop and the step of fixing, mutually and in definitive manner, the surface portions of the portions of the tubular and engagement stem portions.   
     
     
         6 . Method, according to  claim 5 , characterized by the fact that the assembly of the second portion of the connecting rod, in the interior of the cylinder of the compressor, is carried out by its radial displacement through a longitudinal slot, laterally and superiorly provided in the cylinder. 
     
     
         7 . Method, according to  claim 6 , characterized by the fact that the second portion of the connecting rod incorporates a smaller eye that is attached to the piston by means of a pin inserted through the longitudinal slot of the cylinder. 
     
     
         8 . Method, according to  claim 1 , and the cylinder formed by a liner fixed to a respective hole of the block of the compressor, characterized by the fact that the piston is mounted in the second portion of the connecting rod prior to the step of engaging the engagement stem portion in the interior of the tubular stem portion, being said step of engaging and the further step of conducting the tubular and engagement stem portions to a predetermined condition of axial and rotational alignment and relative axial and preliminary positioning performed with said stem portions and piston outside of the compressor, wherein the method further comprises, after the step of shaping the tubular stem portion the steps of:
 mounting the first portion of the connecting rod and the second portion of the connecting rod, already fixed to the piston on the eccentric pin and in the interior of the hole of the block, respectively, with the eccentric pin held in the lower dead point condition;   inserting the liner into the hole of the block, wearing it on the piston prior to the step of rotating the crankshaft of the compressor to bring the eccentric pin to the upper dead point condition, seating the piston against the stop and the step of engaging, mutually and in definitive manner, the surface portions of the tubular and engagement stem portions.   
     
     
         9 . Method, according to  claim 1 , characterized by the fact that the first portion of the connecting rod comprises an larger eye to be mounted on the eccentric pin of the crankshaft of the compressor, and one of the tubular and engagement stem portions, wherein the second portion of the connecting rod comprises, the other of said tubular and engagement stem portions and one of the elements defined by a smaller eye and a spherical joint for coupling to the piston. 
     
     
         10 . Method, according to  claim 8 , characterized by the fact that the outer contour of the engagement stem portion and the inner contour of the tubular stem portion are circular, defining together, an annular space at least partially filled with the fixation mean. 
     
     
         11 . Method, according to  claim 10 , characterized by the fact that the radial deformations, the tubular stem portion, are angularly spaced from each other in each circumferential alignment. 
     
     
         12 . Method, according to  claim 10 , characterized by the fact that it includes the additional step of providing at least one of the parts of the engagement stem portion and tubular stem portion with the fixation mean prior to the telescopic and definitive fixation between said stem portions. 
     
     
         13 . Method, according to  claim 10 , characterized by the fact that the tubular and engagement stem portions have surface portions thereof, adhered to each other, in definitive manner, defined in at least part of at least one of the regions defined between said stem portions.