FR2580049A1 - Damping device for a hanging rotary shaft - Google Patents

Abstract

The dampers 2 which are the subject of the patent application are intended to reduce the amplitudes of movements of revolving machines. They are based on the "squeeze film" principle which develops large damping forces when the piston is moved in the cylinder, either axially or laterally. In the case of lines of vertical shafts 1 moving in a pendular fashion on a swivel, the piston is securely fastened to the male part 5 of the swivel whilst the cylinder is securely fastened to the female part 6 or vice versa. The return forces to the vicinity of the equilibrium position are very low: the alignment function of the swivel may thus easily be fulfilled. The piston is locked during transport, assembly, and maintenance operations by elastomer pads or springs distinctly less stiff than the springs pressing the moving plates onto their stops.

Description

I - PRESENTATION OF THE PROBLEM
I.1 - Introduction
The shaft line of a pendulum rotary machine consists essentially (see Figures 2 and 2bis) - of a shaft (1) driven at its upper part by a rotor
electric and driving at its lower part the rotor of
process (centrifuge bowl, compressor rotor, rotor
turbine, etc ...), not shown, - a bearing comprising 2 bearings (3) and (4) integral with
the male part (5) of a swiveling ball joint inside
the female part (6).

Under the effect of the weight of the rotor, the contact between the male and female parts takes place at A. Under the effect of centrifugal forces, the shaft therefore tends to move laterally inside the horizontal clearance. On the other hand, when the displacements become important, the male patella oscillates around its center.

It very often happens that the amplitudes of the male patella become very large, especially when passing critical speeds and in case of instabilities (divergent spiral instability). It is therefore important to add shock absorbers (2H and 2V) whose aim is to reduce the amplitudes.

The rubber spring connection not shown in Figures 2 and .2 bis between male and female parts fulfills this function. But experience shows that in many cases it is insufficient. The purpose of the shock absorbers, the object of this patent, is to make up for the shortcomings of existing elastic systems. They are based on the principle of "approximation effect".

I.2. Principle of the invention a) principle of 1 "approximation effect" (Figures 3 and 4)
When the piston (7) approaches the fixed part (9) at a speed V, the oil (8) or any other fluid trapped in the annular space between the piston and the fixed part is expelled outward. In this movement, pressure forces arise. These forces F oppose the displacement of the piston thus creating the desired damping.

The report
F c =
v is characteristic of the shock absorber. The sizing, the clearances and the quality of the oil are chosen according to the desired value c.

The clearance to the right of the oil film is generally low. However in the event of instability, it can happen that displacements become much more important. It is therefore necessary to provide additional travel; these are obtained by moving the plate (see Figure 3).

For low speeds v, that is to say, for small displacements of the piston, the plate (9) pressed by the springs (11) on the stop (10) remains stationary. On the other hand, when the displacements become significant, the clearance h becomes very small, the force F then becomes very large and causes the displacement of the plate by compression of the springs.

When the speed v changes direction, the force F disappears and the plate returns to its position against the stop.

b) principle of the hydrodynamic damper with movable plate and double approach effect "of figure 4
In the double "bringing together effect, the two faces of the piston play an identical role. The factor c is thus doubled.

c) use of spring housings to increase
the amortization of figure 5
In the event of large displacements, the oil trapped in the spring housing develops forces which are added to the "approximation effects" already mentioned (parts (14) and (15).

II - DIFFERENT EMBODIMENTS (Figures 2 or 2a)
The shock absorbers can work either horizontally or vertically. In the horizontal position, we first work inside the horizontal clearance; efficiency is increased.

II.1 Description of the hydrodynamic damper with movable plate and double "approach effect" of figure 6
The piston (7) moves in the clearance h when the force F is less than the application force developed by the springs
(11) on the set.

When the force F becomes greater than the force developed by
the springs, the movable plates (9) s1 erase and authorize
large displacements of the piston (safety role).

It therefore appears that, in the vicinity of the equilibrium position, the stiffness of the system is zero and the alignment function which the ball joint must provide can thus be fulfilled easily. Only solid friction is to vatnere to the right of the male and female parts of the patella.

The lower spring (4) struggles inside a housing which guides it and contributes to the "classic viscous effect"
("dash pot") which can be increased by adding pieces
(lit) and (15) of figure 5.

The upper spring struggles along the piston which guides it.

During the transport and assembly phases, it is imperative that the piston is locked in its equilibrium position (equal clearances on both sides of the side faces). This blocking is ensured by the elastomers 10 and it or by springs. It can also be provided by a stirrup 20
The filling openings not shown in the figure are provided.

The piston is sealed (18) either by sliding seals, or by a membrane or any other commercial device.

II.2 DESCRIPTION OF THE HYDRODYNAMIC SHOCK ABSORBER WITH HO SHELF
BILE AND DOUBLE CLOSING EFFECT "IN A BOX OF THE
FIGURE 7
Figure 7 is identical to Figure 6 except that the following two functions have been separated - "close-up effect" ensured inside a box
waterproof, - safety ensured by the same springs that hold the
two trays against the stops. The distance between stops is
equal to the thickness of the mobile housing.

NOTE: the housing has stops to position the plates in position.

II.3 DESCRIPTION OF THE HYDRODYNAMIC SHOCK ABSORBER WITH HOBILE TRAY AND "DOUBLE APPROXIMATION" IN A BOX OF THE
FIGURE 8
Figure 8 is identical to Figure 7 except that the stops have been removed and the equilibrium position is that of the two springs.

II.4 DESCRIPTION OF THE HYDRODYNAMIC SHOCK ABSORBER WITH HOBILE TRAY AND "DOUBLE APPROXIMATION" IN A CRANKCASE
FIGURE 9
Figure 9 is identical to Figure 8 except that the two springs have been placed in a housing of the housing (12) separate from that of the hydrodynamic damper. This means of assembly is not exclusive.

NOTE: the two functions "reconciliation effect" and security "have been separated.

II.5. DESCRIPTION OF THE HYDRODYNAMIC SHOCK ABSORBER WITH "EFFECT OF
"ANNULAR APPROXIMATION BETWEEN PISTON 7 AND CYLINDER 17
OF FIGURE 10
In the preceding shock absorbers, the "approximation effect" takes place between the flat faces of the piston and the plates. In this case, the "approximation effect" takes place in the annular space which separates the piston (7) from the cylinder (17) (see figure n "10).

The principle of the annular "approximation effect" is identical to that of the planar "approximation effect": when the piston moves laterally, the oil trapped in the annular space moves both horizontally and vertically.

Due to the viscosity of the oil, damping forces analogous to the force F in FIG. 2 arise.

To allow significant travel at the passage of critical speeds and in case of instability, the cylinder (17) is secured to the cylinder (12) by means of 2 o-rings (11)
To allow centering of the piston during mounting operations, springs (13) are provided.

As in Figure 2, the piston is secured to the movable part of the ball joint and the cylinder (12) is secured to the fixed plate or vice versa.

The o-rings can be replaced by springs (11) whose calibration is adjustable by means of screws accessible from the outside not shown in the figure.

The seal is ensured by the membrane (18)

Claims (10)

The claims of this patent are characterized by III CLAIMS  1. the damper which is the subject of the patent is based on the principle of  the reconciliation effect, single or double ("squeeze film").  birth during this movement.  and in that it uses the pressure forces taking  approaches a fixed part at a speed v in a fluid  It is characterized in that it consists of a piston which  2. Damping device according to claim 1 characterized in  what the trays held in place by springs against  stops clear when deflections become  important when shifting critical gears and when  instability,  3. Damping device according to claim 1 characterized in  what the positioning can be either horizontal or  vertical, or any other intermediate position. In the  horizontal positioning, the shock absorber begins to work  as soon as the male patella moves radially inside  the female patella. This increases the efficiency of  the damper near its equilibrium position. The  alignment function of the ball joint is then fulfilled so  easy.  4. Damping device according to claim 1 characterized in  what spring or elastomer blocking systems are  intended for all transport and assembly operations.  which press the movable plates on their stop.  Their stiffness is significantly lower than that of the springs 5. Damping device according to claim 1 characterized in  that the shock absorber housing is integral  either the concrete block (19): this solution avoids  couplings,  either from the machine frame (19). In this case, it is  essential that the attachment is sufficiently rigid  so as not to introduce parasitic mode. 6. Damping device according to claim 1 characterized in  what spring housings contribute to damping  thanks to the classic viscous effect. 7. Damping device according to claim 1 characterized in  what the oil circulations along the side faces of the  piston also contribute to conventional viscous damping. 8. Damping device according to claim 1 characterized in  what elastomers and blocking springs can  possibly be replaced by devices of the type  stirrup. In the case of the shock absorber of FIG. 10, the claims are identical to the preceding ones, assuming that the axial displacements of the piston are replaced by radial displacements.  plane of the piston and the bottom of the cylinder.  classic viscous and the "approximation effect" between the face  inner cylinders are also cushioned by the effect  what the relative axial displacements between the piston and the In this case, the additional claims are 9. Damping device according to claim 1 characterized in 10.Damper device according to claim 1 characterized in  what balance holes not shown between the part  upper and lower part of the piston are provided and  avoid overpressure.  SUMMARY OF INDICES 1 rotating machine shaft 2V vertical shock absorber subject of the patent 2H vertical shock absorber subject of the patent 3 upper bearing 4 lower bearing 5 male part of the ball joint 6 female part of the ball joint 7 piston 8 oil film 9 semi fixed plate 10 stops 11 springs 12 shock absorber housing 13 adjustment and transport housing 14 spring guide 15 guide stop 16 shoulder 17 semi-fixed cylinder 18 sealing 19 machine housing or concrete block