WO2001029439A1

WO2001029439A1 - Twin-disc cage for roller bearings

Info

Publication number: WO2001029439A1
Application number: PCT/IT2000/000414
Authority: WO
Inventors: Gabriele Pecorari
Original assignee: SAI Societa Apparecchiature Idrauliche SpA
Current assignee: SAI Societa Apparecchiature Idrauliche SpA
Priority date: 1999-10-19
Filing date: 2000-10-16
Publication date: 2001-04-26
Anticipated expiration: 2002-04-19
Also published as: IT1310859B1; ITMO990232A1; ITMO990232A0

Abstract

The twin-ring cage comprises a ring with a diameter (Dg) which is greater than the diameter (De) of the outer race, having indents (2) in which the rollers (3) are positioned, the two parts being made up of two identical rings (1) with indents (2), each ring having a cut (4), to enable the rings to be assembled misaligned; also, the said two parts being inserted in the same circumferential seat (15) central to the row (F) of rollers (3) with misalignment of the position of the said cuts (4) such that at least one roller (3) is included between them. The said cage is advantageously used in full complement bearings positioned on the eccentric (G) of the crankshaft (7) of radial cylinder (8, 9) hydraulic machines.

Description

TWIN-DISC CAGE FOR ROLLER BEARINGS

Twin-ring cage for roller bearings and radial cylinder hydraulic machine equipped with such a bearing, that is, a special arrangement of the spacer device for the rollers that enables an effective separating action to be achieved whilst keeping the distance between the rollers to a minimum and which facilitates assembly even on integral rings used with hydraulic machines with radial cylinders .

The state of the art comprises cages for the rollers of bearings of various forms which position successive bearings at a distance which is non zero and greater. Also known in the field of roller bearings are spacer rings for rollers with an external diameter greater than the diameter of the outer race, the inner diameter being formed so as to constrain the rollers assigned to it; a seat is created in the said race and, to enable assembly, the outer ring of the bearing is divided into two semi-rings which, in the median zone of contact have the said seat.

In hydraulic machines , in particular in radial cylinder machines, the high loads that the pistons transmit to the crankshaft are generally carried by means of full comple- ent roller bearings; the distribution of the rollers between the two races is achieved with cages, to achieve a high load capacity and reduced dimensions, in order to obtain hydraulic machines of reduced dimensions which transmit high powers . Radial cylinder machines have been devel- oped so as to be used at higher speeds of rotation, whilst maintaining bearings with reduced dimensions . Consequently, the distribution of the rollers varies in function of the speed of rotation of the crankshaft: the rollers, due to the necessary play between the between races, group up in the position which is radially most distant to the axis of rotation, that is, in proximity to the upper dead point, where the inversion of the load occurs, the said rollers being thus subjected to sudden and almost instantaneous variations of load from zero to full load, with the consequence that they knock against each other, they remain in contact with each other and, being prevented from achieving immediate reciprocal equidistance , they are squashed under the operating load, they instantly become oval in shape and act with sliding friction in the absence of rotation for up to half of a revolution past the upper dead point. As a result the rollers and the races deteriorate rapidly causing the seizure of the hydraulic machine. Roller cages according to the state of the art do not enable the dimensions of the races to be reduced, with a view to reducing overall dimensions, and they may not be employed in radial machines, in as much as it is not possible to separate the outer ring in two halves when it is made as one piece with the annular spherical support surface of the said pistons: the sealing action of the said surface would be missing .

The said state of the art may be subject to consider^¬ able improvement with the possibility of inventing a new type of cage which enables the assembly of internal rings whilst ensuring the correct spacing between successive rollers at a distance reduced as far as possible, in the construction of full complement roller bearings .

From the foregoing emerges the need to resolve the technical problem of inventing a new form of spacer cage for rollers, which may be assembled in the outer ring made of one piece, such as used in radial machines.

The invention resolves the said technical problem by adopting: a twin-ring cage for roller bearings , comprising a ring with a diameter which is greater than the diameter of the outer race, having indents in which the rollers are positioned, the two parts being made up of two identical rings with indents, each ring having a cut enabling their misalignment during assembly; furthermore, the said two rings being inserted in the same circumferential seat central to the row of rollers with misalignment of the position of the said cuts such that at least one roller is included between them.

Also adopting, in a preferred embodiment: a roller bearing equipped with at least one twin-ring cage, comprising a ring with a diameter which is greater than the diameter of the outer race, having indents in which the rollers are positioned, the two parts being made up of two identical rings with indents, each ring having a cut ena- bling their misalignment during assembly ; furthermore, the said two rings being inserted in the same circumferential seat central to the row of rollers with misalignment of the position of the said cuts such that at least one roller is included between them. Adopting in a further preferred embodiment : a radial cylinder hydraulic machine equipped with roller bearing, the said roller bearing comprising at least one twin-ring cage having a ring with a diameter which is greater than the diameter of the outer race, having indents in which the rollers are positioned, the two parts being made up of two identical rings with indents, each ring having a cut enabling their misalignment during assembly; furthermore, the said two rings being inserted in the same circumferential seat central to the row of rollers with misalignment of the position of the said cuts such that at least one roller is included between them.

The advantages obtained with this invention are: the rollers are properly spaced and the form of the cage ena- bles the said distance to be reduced to little more than their diameter, thus achieving the full complement of rollers; furthermore, the cage may be employed between the crankshaft and the ring with spherical surface of radial cylinder hydraulic machines, that is, without dividing the said ring into two halves as with prior technique. The hydraulic machine thus obtained has highly innovative tech^¬ nical characteristics which enable the power transmitted to be increased significantly with respect to the original design.

Some embodiments of the invention are illustrated, purely by way of example, in the two tables of drawings attached in which Figure 1 is a view of the cage as described, also showing three rollers positioned by the cage and comprised between the two roller races; Figure 2 is a section of just the crankshaft of a radial cylinder hydraulic machine, with full complement bearing having three rows of cylindrical rollers and cages as described in the present invention; Figure 3 is a photographic representa- tion of the same crankshaft, with the rollers of the third row partially assembled and with the cages as described in the present invention.

The Figures show: 1, Figure 1, the individual spacer ring, with indents 2 for rollers 3; Di , the inner bearing race; De the outer bearing race; Dg the outer diameter of the ring 1; 4, a cut in the ring; 5, Figure 2, the casing of the hydraulic machine; 6, the shaft bearings of the crankshaft 7 with eccentric G; 8, the radial cylinder and 9, its piston; 10, the sealing elements, in their entirety, of the pistons 9 on the spherical surface S, made as a single piece with the outer ring 11 of the bearing; 12, the axial retaining rings of the rollers and 13 the spacer rings between the rows F of bearings 3; 14, the connecting section for the transmission of the torque between the ec- centric and the and the shaft; 15 the annular indentation on the centre-line of each row of rollers, in which the twin-ring cage 1 with cuts 4 is positioned: the two cuts are conveniently positioned at least 1/3 of a revolution f om each other .

The assembly of the bearing equipped with the new cage occurs as follows: having positioned on a level the outer ring with the crankshaft G inside it, the first pair of rings is introduced, one at a time, reducing its diameter by misaligning the respective ends of the cut 4 and inserting it in the predetermined annular indentation 15; the relative angular position of the two rings placed in the same indentation is adjusted by rotating sliding one with respect to the other so as to obtain, conveniently, at 1/3 of a revolution; the operation of insertion may be carried out more conveniently from the opposite side of the connecting section 14 inserting individual rollers in the indents 2; at the same time a separator ring 13 is placed before and after a row F of rollers 3; subsequent rows 2a and 3a are similarly assembled and finally the axial retaining ring 12 is positioned.

The operation of such a bearing proves to be very effective, whereby the central cage, although made up of two elements 1 functions as a single cage keeping each roller 3 at a fixed predetermined distance from the next one: the cut in each of the two rings does not influence the said distance, in as much as the cage is in two parts and the said cuts, as said, are not positioned in correspondence with the same roller, the two cuts 4 being position no closer than in correspondence with three contiguous roll^¬ ers, so that at least one roller is secured by both rings, but preferably being positioned as far apart as possible . Finally, a radial cylinder hydraulic machine equipped with such a bearing has a considerable aptitude for high speed operation; test carried out show that with a prior art full complement bearing without cage, the knocking phenomenon described previously occurs when the tangential speed of the race Di (on the crankshaft) reaches 2 m/s; with the bearing equipped with the twin-ring cage 1 as described in the invention, however, it is possible to reach a speed of 8 m/s. Therefore, as the power transmitted is proportional to the square of the speed of rotation, the same hydraulic machine may transmit up to 16 times the more power. in practice the materials, the dimensions and details of execution may be different from, but technically equivalent to, those described without departing from the juridical domain of present invention.

Claims

1. Twin-ring cage for roller bearings, comprising a ring with a diameter (Dg) which is greater than the diame- ter (De) of the outer race, having indents (2) in which the rollers (3) are positioned, characterised in that the two parts are made up of two identical rings (1) with indents (2) , each ring having a cut (4) enabling misalignment during assembly; furthermore, the said two rings are inserted in the same circumferential seat (15) central to the row (F) of rollers (3) with misalignment of the position of the said cuts (4) such that at least one roller (3) is included between them.

2. Roller bearing equipped with at least one twin-ring cage, comprising a ring with a diameter (Dg) which is greater than the diameter (De) of the outer race, having indents (2) in which the rollers (3) are positioned, characterised in that the two parts are made up of two identi- cal rings (1) with indents (2) , each ring having a cut (4) enabling misalignment during assembly; furthermore, the said two rings are inserted in the same circumferential seat (15) central to the row (F) of rollers (3) with misalignment of the position of the said cuts (4) such that at least one roller (3) is included between them.

3. Radial cylinder hydraulic machine (8, 9) equipped with roller bearing, characterised in that the said roller bearing is equipped with at least one twin-ring cage (1) , comprising a ring with a diameter (Dg) which is greater than the diameter (De) of the outer race, having indents (2) in which the rollers (3) are positioned; the two parts are made up of two identical rings (1) with indents (2) , each ring having a cut (4) enabling misalignment during assembly; furthermore, the said two rings are inserted in the same circumferential seat (15) central to the row (F) of rollers (3) with misalignment of the position of the said cuts (4) such that at least one roller (3) is included between them.