ITTV20060206A1 - HOLDING DEVICE. - Google Patents

Description

DESCRIPTION OF INDUSTRIAL INVENTION

With the title: SEALING DEVICE

On behalf of: Ros Giovanni Battista

Filed with number

Designated inventor: Ros Giovanni Battista sf DESCRIPTION

The technical problem to be solved is described with an example:

in motors and vane compressors (fig. 1), one of the important loss factors is the gas leakage between rotor and casing in

correspondence of the circumferences coupled on the two sides.

Currently, the following systems are used to limit this drawback: A a) Front seal using machining with restricted tolerances: this system does not allow to compensate for thermal expansion, which is added to dimensional tolerances.

b) Front seal by adopting surface! floats pressed against the rotor by springs: this method introduces a brake on the rotor, with difficulty obtaining and maintaining the optimal compromise between friction losses and volumetric losses.

c) Peripheral labyrinth seal: its critical point is in the eccentricity between

rotor and fixed seat, which makes it necessary to keep play more relevant than those possible with an exactly centered coupling.

TV 2006 A 0002 06

The device object of the present patent application, represented in fig. 2 and fig. 3 of Table 1, consists of:

♦ Fixed ring (detail 1).

♦ Self-compensating ring (detail 2).

♦ Containment ring for the self-compensating ring (detail 3).

♦ Separation and towing plates (detail 4 of fig.2 and fig.3). Possible.

Note:

• The fixed ring has the function of interfacing with the self-compensating ring

constituting the preferably, but not exclusively, cylindrical surface of the meatus that is created between the two,

• The self-compensating ring has the outside preferably, but not exclusively, conical. On this surface it is possible to obtain one or more grooves <"> Λ with the function of reducing losses due to viscous friction.

The interior has a width reduced by a step. On the internal surface or on the sides it is possible to obtain notches, grooves and other shapes for towing in synchrony with the

ring nut and / or to improve sealing on the ring nut side.

* The main function of the ring nut is to contain the axial thrust on the self-compensating ring with a surface that guarantees the seal while allowing the ring itself to slide. It can also provide the seat for the separation plates. It can be threaded, keyed or, in another way, made integral with the rotor.

• The separation plates, pressed by centrifugal force, divide the space between the self-compensating ring and the ring nut into sectors, giving, where provided, the

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certainty that, sector by sector, the pressure under the ring is exactly that existing in the facing machine sector.

• The separation function is actually used in cases where it is

deviation from the static value pj of the pressure under the ring, due to flow in the meatus between the self-compensating ring and the ring nut is not effectively

compensated by the forces that stabilize the ring in a favorable position.

• The foils can also carry out the driving function of the ring, where yes

deems it appropriate to synchronize it with the ring nut (fig. 3).

• Sealing of the self-compensating ring towards the ring nut and / or towing can, in

alternatively, be ensured by the interposition of an O-ring in a groove

obtained between the ring nut and the self-compensating ring.

• The meatus between the fixed ring and the self-compensating ring can have a specular section, thus becoming the internal surface of the fixed ring shapes the external surface of the cylindrical self-compensating ring.

The meatus between the fixed ring and the self-compensating ring can be obtained partly on the self-compensating ring and partly on the fixed ring.

• The fixed ring can possibly be integrated into the case.

• The ring nut can be partially or completely integrated into the rotor.

• The device can be made in a specular way, thus becoming the containment ring integral with the case, the fixed ring integral with the rotor, the self-compensating ring with shaped internal surface and external with reduced width by a step.

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Operation

With reference to Fig. 2: Self-compensating Linear (2) performs the seal towards fixed Linear (1) thanks to a limited clearance on the diameter. In the axial direction the internal pressure more presses Fanello (2) against the ring nut (3) (surface a

lapped contact) ensuring the seal on this side while allowing

scrolling.

In the radial direction, sector by sector, the following situation occurs: pressure

more than, by way of example but not exclusively, acts on 75% of the

ring width, pressure p2 on the remaining 25%, with an average internal pressure:

p, = P2 + 0.75 (pt - pj)

Considering the laminar fluid motion in the meatus between the two rings, the

mean external pressure p and is a function of t2 / t [which varies between:

pc- P2 <+> 0.5 (pi - p2) with distance t2 sufficient to consider t2 / ti = l, and: pe = p2 + 1, 0 (pi - p2) when the distance t2 vanishes and, therefore,: t2 / t | -0.

Choose a suitable t2 and the ratio t2 / tj so that it is: pt. = P,,

Self-compensating fanello is positioned concentrically to the fixed one, a

distance t2 = cost, and pc = p, for all sectors.

The ring oscillations are counteracted up to Δρε = ± 0.25 (pi - p2) and, therefore, the position is stable.

This means automatic compensation of eccentricity, due to geometric tolerances, so-called settlement of the bearing axis under load, which is sensitive for example in vane machines.

The distance t2e, therefore, the ideal diameter d2 with zero tolerance, are determined in a theoretical-experimental way as follows:

1) The losses due to residual leaks and viscous friction are expressed as a function of t2e t ,.

2) The ratio t2 / ti corresponding to the ratio (pc-p2) / (pi-p2) desired (e.g. 0.75) is determined to equilibrate pi. At this point the losses become

function of t2 alone.

3) The t2 corresponding to the minimum of the sum of the losses is the value sought.

4) Therefore, ti are obtained from the known t2 / t | ratio and the consequent shape of the self-compensating ring.

If, due to the machining tolerances, the diameter d2 comes to

be less than the ideal one, initially consider the ring centered on the fixed one. The distance will be greater than the ideal t2 and therefore each sector will be attracted to the outside by the stabilizing forces.

In the case of variable pressure along the perimeter, as in motors and vane compressors, the prevalence of forces in the higher pressure sectors causes the ring to be placed in a favorable eccentric position. The calculation, done

with IT6 tolerance, shows a substantial indifference to the sum of the losses already mentioned, i.e. the automatic compensation of tolerances

dimensional by the ring.

In the case of uniform pressure along the perimeter, as in turbomachinery, the tolerances have modest repercussions on efficiency if one remains in a fairly narrow neighborhood of the minimum point.

Preliminary calculations suggest that the device can reduce localized losses on this seal even by an order of magnitude compared to existing systems, removing a serious handicap from some families of machines.

Treviso, 10-11-2006

Claims (12)

ftrt vy r, CLAIMS 1) Sealing device characterized by a fixed ring, self-compensating ring, containment ring nut. 2) Device as per claim (1) in which the fixed panel has the function of interfacing with the self-compensating ring constituting the surface preferably, but not exclusively, cylindrical of the meatus which comes to be created between the two. 3) Device as per the previous claims in which the rotating ring self-compensating has an external surface preferably, but not exclusively, conical, on which one or more grooves can be obtained. The interior has a width reduced by a step. With any trend of the pressure to contain this conformation is such that, associated optionally to the separation of the sectors according to the subsequent claims, at each point the average external pressure equals exactly and in a manner the average internal to the ring itself is stable. In fact, sector by sector, we have the following situation: pressure pi acting on a fraction b of the width of the ring, pressure p2 on the remaining part, with an average internal pressure: pi = p2 + b (pi - p2) The average external pressure pe is a function of t2 / t]: Pe = P2 φ (Pi -P2) with φ = 1 for t2 / t | = 0 and φ = 0.5 for l2 / t | = 1 Choose a suitable t2 and the ratio t2 / t | so that it is: <p = b, the self-compensating ring is positioned concentrically to the fixed one, with pe = p, for all sectors. The ring oscillations are counteracted by: Apc = (b -φ) (pi - p2) [for example up to Δρε = ± 0.25 (pi - p2) if b = 0.75]. Therefore, the position is stable, giving the ring the self-compensation characteristics of eccentricity and dimensional tolerances from which TV 200δ A 00 02 06 takes its name, and which allow, ultimately, to minimize the sum of the losses due to viscous friction and leaks on the seal, also reducing them by an order of magnitude compared to existing systems, 4) Device as per the previous claims in which the ring nut, integral with the rotor, has the main function of containing the axial thrust on the ring self-compensating while ensuring the seal between the contact surfaces and the possibility of sliding the self-compensating ring. 5) Device as per the previous claims in which, in cases where the deviation from the static value pi of the pressure under the ring due to flow in the meatus between the self-compensating ring and the ring nut is not effectively compensated by the stabilizing forces, the presence of the plates of separation that divide the space between the self-compensating ring and the ring nut into sectors, giving the certainty that, sector by sector, the pressure below the self-compensating ring is exactly that existing in the facing machine sector. The seats for the separation plates can be obtained on the ring nut or, alternatively, directly on the rotor. 6) Device as per the previous claims in which the separation plates, where provided, can also perform the driving function of the self-compensating ring, where it is appropriate to synchronize it with the ring nut. 7) Device as per the previous claims in which the sealing of the self-compensating ring against the ring nut and / or the drive is ensured by the interposition of an O-ring in a groove formed between the ring nut and the ring, 8) Device according to the previous claims in which the shape of the meatus between the fixed ring and the self-compensating ring can be mirrored, becoming therefore, the outer surface of the cylindrical self-compensating ring and the inner surface of the shaped fixed Fanello. 9) Device according to the preceding claims in which the meatus between the ring fixed and self-compensating ring can be obtained partly on the self-compensating fanello and partly on the fixed ring. 10) Device as per the preceding claims in which fixed Fanello can be integrated into the casing. 11) Device according to the preceding claims in which the ring nut can be partially or completely integrated in the rotor. 12) Device as per the preceding claims made in a mirror-like manner, thus becoming the containment ring integral with the casing, fixed Linear integral with the rotor, self-compensating Linear with shaped internal surface and external with reduced width by a step. Treviso, 10-11-2006