FR2545546A1 - CRANKSHAFT FOR HERMETIC COMPRESSORS FOR REFRIGERATORS AND THE LIKE - Google Patents

Abstract

THE CRANKSHAFT 5 FOR HERMETIC COMPRESSORS ACCORDING TO THE INVENTION INCLUDES A TUBULAR PART 8 AT THE LOWER END OF WHICH A TUBULAR NOSE 9 IN PLASTIC MATERIAL IS FIXED UPWARDS. THE NOSE 9 IS INTENDED TO SUCK THE LUBRICANT FROM THE BOTTOM OF THE COMPRESSOR SHELL AS A RESULT OF THE ROTATION OF THE CRANKSHAFT 5 AND DELIVER IT TO THE TUBULAR PART 8 OF THE CRANKSHAFT 5 ITSELF. AT ITS LOWER END, THE TUBULAR PART CONTAINS AN EXTERNAL CIRCULAR THROAT 16 WHOSE LOWER TRUNCONIC SIDE CONVERTS UPWARD. THE UPPER PART OF THE NOSE SHAPES A SLEEVE 18 SLEEVE ON THE LOWER END OF PART 8. THE INNER WALL OF THE SLEEVE HAS TEETH-SHAPED PROJECTIONS COOPERATING LIKE A CAM WITH THE TRUNCONIC SIDE OF THE THROAT TO PUSH THE THROAT. NOSE 9 UP AS A RESULT OF THE ELASTICITY OF SLEEVE 18, UNTIL A FLUID-TIGHT COUPLING POSITION WITH THE LOWER END OF TUBULAR PART 8.

Description

Crankshaft for hermetic compressors intended for refrigerators and

  The present invention relates to hermetic compressors and relates particularly to a crankshaft

  for hermetic compressors intended to be installed vertically

  wedging in the casing of the compressor and comprising a tubular part comprising, at its lower end, a tubular nose made of plastic material which comprises an upper part engaged on the tubular part and a lower part diverging upwards to suck up the lubricant

  in the bottom of the envelope and to deliver it, through the

  crankshaft, to lubrication lines

  formed in an upper part of the crankshaft itself.

  A crankshaft of the type specified above is known

from US Patent 4,209,080.

  In this known solution, the plastic nose is constituted by a tubular part formed by two parts,

  an upper part and a lower part, between the

  what is an external hexagonal collar The lower part diverges upwards and constitutes the nose proper The upper part is divided longitudinally, in the direction of its upper end, into two opposite elastic arms each of which carries an outer tooth diametrically opposite to the other tooth The collar has two projections

  diametrically opposite on its upper face.

  The tubular part of the crankshaft is provided, at a certain height, with a pair of diametrically opposite lateral holes intended to receive the teeth and, in the lower edge, with a pair of diametrically opposite notches intended for

receive the projections.

  The nose assembly is carried out by introducing the elastic arms into the tubular part of the crankshaft and then orienting the nose by means of the hexagonal collar until

  that the projections come in alignment with the notches.

  During this orientation, the part is completely pushed

  upper part of the nose in the tubular part of the crankshaft.

  The projections then engage in the notches and the teeth snap into the sides, thereby ensuring the anchoring of the nose. This known solution has two drawbacks. A first drawback resides in the fact that, in order to obtain coupling by engagement, it is necessary to carry out three movements, namely, firstly, an axial movement of insertion of the arms into the part tubular, then alignment with the side holes and, finally, a

  additional axial movement to complete engagement.

  A second disadvantage lies in the quantity considered.

  plastic material needed to form the part.

  The upper tubular part must, in fact, be long enough to avoid sealing problems given the oil pressure which is maximum at the end.

  lower part of the tubular part of the crankshaft.

  The object of the present invention is to obtain a plastic nose of the type mentioned above, which requires a simple axial movement for its engagement, with as a consequence a corresponding saving in labor and / or in cost of material, and which does not raise problems of tightness with respect to the pressure in spite of the small quantity of plastic material used for its manufacture, with for

  consequently a corresponding saving of matter.

  The crankshaft according to the present invention is characterized

  laughed at by the fact that the tubular part comprises, at its lower end, an external circular groove and that the upper part of the nose is constituted by a circular sleeve which is elastically expandable and which is fitted on the lower end of the tubular part and has a circular crown> projecting inwardly interlocked in the groove and of which a lower side bears against a corresponding lower side of the groove, and by the fact that, in the transition zone between the lower part of the nose and the sleeve is finds an upwardly directed radial inner circular shoulder bearing against the lower edge of the tubular part, and that at least one of the lower sides has a frustoconical shape as a whole which converges upwards so as to exert, in cooperation with the other lower side, a cam action to convert the elastic contraction force of the sleeve into an axial pressure of said

shoulder against said edge.

  The invention thus makes it possible to form a crankshaft which does not have the drawbacks of similar devices of the prior art and which has a structure making it possible to manufacture it easily, conveniently and economically. The present invention will now be described purely by way of non-limiting illustration with reference to the accompanying drawings, in which s

  Figure 1 is a partial side elevational view-

  Lately torn from a hermetic compressor which is intended for refrigerators and which is provided with a crankshaft according to the present invention; Figure 2 is an exploded perspective view of a crankshaft according to the present invention; Figures 3 and 4 are two views in axial section of the lower part of the crankshaft of Figure 2 illustrated respectively before and after assembly; and FIG. 5 is a view of one of the elements illustrated in FIGS. 2 to 4 above. In the drawings, a hermetic compressor intended for refrigerators is generally designated by the

reference 1.

  The compressor illustrated is substantially similar to the compressor described in the Italian patent application

  No. 68090-À / 81, the description of which is incorporated herein

set out for reference.

  The compressor t comprises a hermetic envelope 2 made of sheet metal in which a motor-compressor block referenced 3

  as a whole hangs elastically.

  A profiled element 4, preferably of cast iron, constitutes the body of the block 3 It can be seen that the magnet 4 comprises a central tubular body with a vertical axis acting

  as a bearing vis-à-vis the crankshaft 5.

  The crankshaft 5 (FIG. 2) comprises, as main part, successively from the upper end to the lower end, a crank pin 6, an eccentric 7 in the form of a flattened sector, a tubular intermediate part 8 and a nose tubular diverging upwards and

referenced 9.

  The upper section of the tubular part 8 is coupled for rotation in said bearing In addition, the underside of the eccentric 7 has an annular raised part 10 which cooperates in the form of a thrust bearing with a surface raised annular upper It

of the landing.

  On the lower section of the tubular part 8 is wedged, by means not shown, the rotor 12 of an electric motor whose stator is fixed at its lower end to the profiled element (body) 4, To the crankpin 6 is coupled the head of a connecting rod 13, the other end of which is assembled with a piston which can slide in the cylinder of a compressor arranged in the part

top of the envelope.

  The lower end of the nose 9 plunges into a lubricant 14 located in the lower part of the casing 2 During the rotation of the crankshaft, the nose 9 acts in a known manner as an axial centrifugal pump causing the lubricant to rise towards eccentric 7 and

  crankpin 6 through the tubular part 8.

  In the tubular part 8, the eccentric 7 and the manteon 6 are lubrication holes, some of which,

  visible in Figures 1 and 2, are referenced 15.

  Normally, the crank pin 6 and the eccentric 7 are formed in one piece and are made of sintered metal However, the tubular part is formed of a piece of tube which can be cut from a continuous calibrated tube of mild steel of medium quality. The tubular part 8 is assembled with the eccentric 7 and the crank pin 6 by engaging the upper end of the part

  8 in the seat delimited by the raised annular part 10.

  Once this engagement has been carried out, the preferred method to obtain the final union between the two parts is the welding by boss or with compression Another method of assembly is the bonding using a structural adhesive

for metals.

  As can be better seen in Figures 3 and 4, the tubular part 8 has a circular groove 16 at its lower end The groove 16 has a triangular profile with a lower frustoconical side 16 a converging upwards. The neck 9 includes a lower conical portion 17 diverging upwards and above which is located

a sleeve 18.

  In the transition region between the conical part 17 and the sleeve 18, the inner wall of the nose 9 has

  an annular shoulder 19 oriented upwards.

  The shoulder 19 has a dimension corresponding to the dimension of the bottom end face 20 of the part

tubular 8.

  Two fins referenced 21 extend axially in diametrically opposite positions inside the

conical part 17 of the nose 9.

  The fins 21 act in a known manner as vanes to propel the lubricant 14 drawn from the bottom of

  the casing 2 during the rotation of the crankshaft 5.

  This propelling action, which is tangential to the crankshaft 5 together with the divergent shape of the lower part 17 of the nose 9, causes the lubricant to rise inside the tubular part 8 The arrangement is such that the maximum pressure of the lubricant is reached in the transition region between the conical part 17 and the sleeve

18.

  The sleeve 18 has notches or slots 22 which divide it into several curvilinear segments (six in the example

  illustrated) extending vertically from the assembly region

blocking with the conical part 17.

  The nose 9 is formed from a single piece of elastic plastic material such as, for example, polyamide The segments

  curvilinear of the sleeve 18 are therefore elastic and

  put to fit the nose 9 on the lower end of the tubular element 18 Several of the sleeve segments, referenced 23, have at their free ends enlarged heads 24 whose inner faces are provided with tooth-shaped projections 25 having a triangular profile

  substantially identical to the profile of the circular groove 16.

  More particularly, the lower face of each projection 25 is inclined relative to the axis of the crankshaft 5 in a manner identical to that of the lower c 8 tee 16 a of the

throat of the tubular part.

  When the part 9 is inserted on the end

  bottom of the tubular part 8, the projections 25

  engage in the groove 16 then cooperate, in the manner of a cam, with the c 8 frustoconical tee 16 a by pushing the nose 9 towards

the top.

  As a result of this biasing force, the surface of the shoulder: nent 19 comes to bear forcefully against the end face 20 of the tubular part, thus giving a coupling which ensures between the wall of the tubular part 8 and the wall a seal 9 preventing the lubricant from dispersing towards the outside and guaranteeing the maximum efficiency of the pumping action * An elastic ring 26, for example a metal ring

7 2545546

  open, surrounds the sleeve 18 in correspondence with its upper edge The force exerted by the elastic ring 26 is added to the elasticity of the segments 23 themselves to increase the radial thrust which pushes the projections 25 in the groove 16 as well as the the lubrication line

  in the region where the lubricant pressure is maximum.

  Preferably, the head portions 24 of the segments 23 are provided externally with raised edges 27 acting

  as upper stops vis-à-vis the ring 26.

  Other projections 28, acting as lower stops vis-à-vis the ring 26, extend from

  the outer face of the side wall of the sleeve 18.

  Naturally, the general idea of the invention remaining the same as variants and modifications can be made to the above embodiments in the context

of the present invention.

Claims (4)

Rl EVENDICATIONS   1 Crankshaft for hermetic compressors intended to be installed in the casing of the compressor and comprising a tubular part comprising, at its lower end, a tubular plastic nose which comprises an upper part which engages on the tubular part and a lower diverging part upwards so as to draw the lubricant into the bottom of the casing and deliver it,   through the crankshaft, to lubrication lines   cation formed in an upper part of the crankshaft itself   same, characterized in that the tubular part (8) has, at its lower end an external circular groove (16) and that the upper part of the nose (9) is constituted by a circular sleeve (18) which is elastically expandable and which is fitted on the lower end of the tubular part (8) and is provided with a circular crown projecting inwards 9 engaged in the groove (16) and whose c 8 lower tee bears against a corresponding lower side (16 a) of the grooves and by the fact that in the transition zone between the lower part (17) of the nose (9) and the sleeve (18) there is an inner radial circular shoulder (19) oriented upwards and bearing against the lower edge (20) of the tubular part (8) and that at least one (16a) of the lower sides as a whole has a frustoconical shape converging upwards so as to exert, in cooperation with the other c 8 lower tee, a cam action to convert the elastic tensile force of the sleeve (18) at an axial pressure of said shoulder (19) against said edge (20).   2 Crankshaft according to claim 1, characterized in that an elastic ring (26) is mounted on the   sleeve (18) and exerts a contraction force which is superimposed   poses the elastic contraction force of the sleeve (18) itself. 3 Crankshaft according to claim t or the 9 2545546   Claim 2, characterized in that the sleeve (18) has several axial slots (22) which divide the sleeve (18) itself into several segments which can diverge elastically and at least some of which (23) bear near their ends free projections (25) in the form of teeth which can engage in the throat   circular (16) of the tubular part (8) of the crankshaft.   4 crankshaft according to claim 3, characterized in that at least some (23) of the elastic segments have at their free ends enlarged head parts (24) forming, on their surfaces oriented towards the inside of the sleeve (19) , tooth-shaped projections (25) which can be engaged in the circular groove (16) of the tubular part (8) of the crankshaft and, on the outwardly facing surface of the sleeve (18), an element   axial stop (27) for the elastic ring (26).   Crankshaft according to any one of the claims   above, characterized in that the nose (9) is provided internally with fins (21) which act as vanes to propel the lubricant.