WO1980001503A1

WO1980001503A1 - A thrust bearing device,particularly for taking up oscillating rotational movements

Info

Publication number: WO1980001503A1
Application number: PCT/DK1980/000003
Authority: WO
Inventors: S Kristiansen
Original assignee: Nordisk Ventilator Co
Current assignee: Novenco Building and Industry AS
Priority date: 1979-01-19
Filing date: 1980-01-09
Publication date: 1980-07-24
Anticipated expiration: 1981-07-19
Also published as: AU5470080A; EP0022832B1; AU528619B2; JPS56500187A; EP0022832A1; SE8006287L; US4346948A; DE3065436D1; GB2052650B; JPH0138330Y2; JPS6260724U; GB2052650A; SE433249B

Abstract

A thrust bearing device, particularly for taking up oscillating rotational movements, for example for use as a blade suspension bearing in an axial flow fan, in which two coaxial thrust bearings which are coupled in series with respect to their loading forces are individually restricted by means of a blocking device to be allowed to turn in one or the other direction of revolution only, so that each roller (3, 4) in each of the two bearings at each rotational movement will be displaced to local engagement against a new point of contact one each of the races (1, 10; 11, 2) in question. The blocking device is constructed to allow stepless relative rotational movement between mutually immovable races (10, 11) in each of the two bearings and one or the other of two relatively movable races (1, 2) belonging to each of the two bearings. The blocking device may be constituted by a spring coupling comprising two helical springs (13, 14), each of which is arranged for exerting spring action on race rings (5, 6, 12) belonging to the same bearing on the internal or the external sides thereof.

Description

A thrust bearing device, particularly for taking up oscillating rotational movements.

Technical field The invention relates to a thrust bearing device, particularly for taking up oscillating rotational move¬ ments of two relatively movable coaxial roller races positioned in parallel planes and axially loaded relative to each other. Background art

Thrust bearing devices of this kind, which are not only exposed to a considerable axial load, but in which only small oscillating rotational movements of one race relative to the other occur in a considerable part of the operational life, are used, for example, as blade suspension bearings for axial flow fans having blades which are adjustable during operation. Usually, the adjustable blades are retained in the wheel rim of the fan wheel by a suspension arrangement, in which a control arm connected with the blade foot and having also con¬ nection with a blade pitch ajusting mechanism, carries a flange which is connected with one race of the bearing, whereas the other race is secured relative to a sur¬ rounding bearing bore in the wheel rim. During rotation of the fan, such blade suspension bearings are exposed to a very heavy axial pressure load from the centrifugal forces acting on the blade. More¬ over, for a given blade pitch setting the rollers of the bearing will be in a nearly stationary condition relative to the races and only perform a small rocking or oscil¬ lating rolling movement around a position of equilibrium in synchronism with control pulses supplied to the blade adjusting mechamism. As a result of these two phenomena taken together, bearings of this kind are to a particu- lar extent subjected to wear, which often results in de¬ terioration of the races due to a phenomenon of surface impression fatigue, also known under the term "brinel- ling", whereby the rollers may be blocked relative to the races, so that the relative movability thereof is reduced or even completely prevented, and adjustment of the blade pitch is considerably restricted or completely blocked.

In spite of continuous efforts to remedy these pro¬ blems for blade suspension bearings through improved bearing design^" and surface treatment of rollers and ra¬ ces, bearings of the kind referred to will, in practice, often suffer from the above mentioned disadvantages.

Similar problems occur in axial thrust bearings of the kind used in the front wheel suspension arrangement of vehicles, such as automobiles for transferring the weight of the vehicle to the rotatably suspended front wheels. Also in such bearings, a risk of brinelling oc¬ curs as a result of the fact that only part of the races of the bearing is utilized.

In this field, it has been suggested in the specifi¬ cation of US Patent No. 2,453,291 to remove the disadvan- tages mentioned by means of a thrust bearing device of the kind mentioned having two relatively movable coaxial roller races positioned in parallel planes and axially loaded relative to each other, said races constituting one of the races of each of two coaxial thrust bearings coupled in series with respect to their loading forces, in which bearings the two opposite races are immovable relative to each other and are prevented by a blocking device from rotating in one and the other direction of revolution, respectively, relative to one and the other of said relatively movable races.

In this prior art bearing design, the two se¬ ries-arranged bearings will be alternatively active for one and the other direction of revolution. When one of the relatively movable races belonging to each of the two bearings is performing a rotational movement, where¬ as the other is retained against rotation, the opposite relatively immovable races belonging to each of the bearings will by movement in one direction of revolution

OMΠ take part in this rotational movement, whereas by move¬ ment in the other direction of revolution they will be retained against rotation. As a result thereof, each roller in each bearing will, in principle, by each rota- tional movement performed by the bearing in question be displaced to local engagement with another part of con¬ tact on the races in question.

Moreover, the design with two bearings coupled in series with respect to their loading forces results in a distribution of wear. Both the continuous displacement of the rollers relative to the races and this distribu¬ tion of the wearing load contribute to a reduction of the risk of brinelling and thereby to an increase of the life time. In the above mentioned prior art design, the block¬ ing device comprises two ratched teeth mechanisms belong¬ ing to each of the bearings and each comprising two rims each connected with one of the race rings of the bearing, said rims being formed with ratched teeth facing and mu- tually engaging each other and designed such that the teeth are oppositely directed in the two ratched teeth mechanisms, which are coupled together by provision of the relatively immovable races on a common intermediate race ring for the two bearings. In addition to the complicated construction, which makes the bearing device considerably more expensive, the above mentioned design of the blocking device in the known bearing construction will only be able to fulfil the object aimed at, i.e. secure a continuous displace- ment of the rollers relative to the races, for rotation¬ al movements beyond a certain magnitude corresponding to the tooth spacing of the ratched teeth rims. In view thereof and of the fact that in case of a great axial load, a considerable resistance must be overcome for each rotational movement due to the engagement of said ratched teeth, the prior art construction referred to will not be suitable for taking up small oscillating rotational movements of the kind occurring, inter alia,

OMPI in blade suspension bearings as mentioned hereinbefore, which are exposed to a very heavy axial load from cen¬ trifugal forces. With the described design of the block¬ ing device in the known bearing construction, such small movements will not give rise to any displacement of the rollers, because they are typically smaller than the mi¬ nimum movement determined by the tooth spacing of the ratched teeth. Disclosure of the invention Without being limited thereto, it is a particular object of the invention to remedy the disadvantages de¬ scribed also for such bearings which as mentioned above are typically exposed to small oscillating rotational movements, so that a continuous displacement of the rollers relative to the races is secured for arbitrarily small movements.

Taking as a starting point the design known from the specification of the above mentioned US Patent, a thrust bearing device according to the invention is characterized in that said blocking device is construct¬ ed to allow substantially stepless relative rotational movement between said relatively immovable races and one or the other of said relatively movable races with¬ out any axial displacement of any part of the bearing device.

In a preferred embodiment of the thrust bearing device according to the invention, the blocking device is constituted by a spring coupling comprising two heli¬ cal springs, each of which is arranged for spring action against two race rings belonging to the same bearing, each of said springs terminating freely at least in one end.

Thus, in this embodiment the blocking mechanism is based on substantially the same principle as s free wheel mechanism. For each of the two directions of revolution, the engagement between one helical spring and one or both of the race rings influenced thereby will be loosened, so that the two races for the bearing in question may

OMP P move relative to each other, whereas the engagement be¬ tween the other helical spring and both of the race rings influenced thereby will be tightened to prevent rotation¬ al movement of the two race rings of the other bearing relative to each other.

In an embodiment, in which the race rings have the same diameter^" for the two bearings, such as known in it¬ self from the specifica ion of the above mentioned US Patent, both of said helical springs may be arranged on the same side of the race rings seen in the radial di¬ rection and with opposite helix directions relative to one another.

If, due to considerations with respect to demands of space, the thrust bearing device is desired to be constructed with a smaller height than obtainable with two series-coupled bearings having the same diameter, which may be desirable in case of blade suspension bear¬ ings, for example, the two bearings may have different diameters and partly overlap each other in the axial di- rection.

If, in connection therewith, the above mentioned design of the blocking device as a spring coupling is used, it is advantageous if one helical spring is arran¬ ged inside the two race rings belonging to one bearing, whereas the other helical spring is arranged outside the two race rings belonging to the other bearing, the two helical springs having the same helix direction. How¬ ever, this different arrangement of the helical springs may also be used in case of two bearings having the same diameter.

In the above mentioned design comprising two bear¬ ings having different diameters, the blocking device may, instead of by means of a spring coupling, be obtained in that the race rings for the relatively immovable races are coupled through a coupling member, which is restrict¬ ed to rotation in a prescribed direction of revolution relative to each of said relatively movable races. Such a coupling member may be coupled with one or the other of said relatively movable races in each bearing through a roller clutch.

Brief description of drawings

In the following, the invention will be explained in further detail with reference to the schematical draw¬ ings, in which

Fig. 1 illustrates the principles of a thrust bear- ing device according to the invention by means of a first embodiment thereof;

Figs. 2 and 3 are an axial sectional view and a side view, respectively, of a design example of the em¬ bodiment shown in Fig. 1; Figs. 4 and 5 are an axial sectional view and a side view, respectively, of a particularly simple and cheap embodiment by modification of the construction ex¬ ample shown in Figs. 2 and 3;

Figs. 6 and 7 are sectional views in an axial plane of the wheel rim for an axial flow fan, in which modifi¬ cations of the embodiment shown in Figs. 4 and 5 are used as blade suspension bearings;

Fig. 8 shows a modification of the embodiment in Fig. 7; Fig. 9 is a sectional view corresponding to Figs. 6 to 8, in which an alternative embodiment of the thrust bearing device according to the invention is used as blade suspension bearing; and

Fig. 10 is a partial sectional view along the lines χ-χ in Fig. 9.

Detailed description

In the schematic illustration in Fig. 1, the rela¬ tively movable races of the thrust bearing devices are

OM shown at 1 and 2. As shown, each of these races constitu¬ tes one race of each of two coaxial thrust bearings, which are series-coupled with respect to their loading forces, said bearings being shown in the figure with rollers in the form of balls at 3 and 4, respectively. The relatively movable races 1 and 2 are constituted in the figure by..the surfaces facing each other and positi¬ oned in radial^" planes of two race rings 5 and 6, respect¬ ively, having the same diameter, one of said race rings 6 being retained against rotation as symbolically indi¬ cated at 7, whereas the other race ring 5 as indicated by arrows 8 and 9 may perform an oscillating rotational movement.

The opposed races 10 and 11, respectively, relative to the races 1 and 2, of each of the two series-coupled bearings are relatively immovable and may, as shown, be constituted by the opposite radial surfaces of a common intermediate race ring 12,

As a blocking device, which in accordance with the invention shall prevent the relatively immovable races 10 and 11 from rotating in one and the other of the di¬ rections of revolution shown by the arrows 8 and 9, re¬ spectively, relative to one and the other of the relati¬ vely movable races 1 and 2, respectively, there is shown schematically in Fig. 1 a spring coupling comprising two helical springs 13 and 14 arranged without any firm con¬ nection on the intermediate ring 12 with the relatively immovable races and each of the race rings 5 and 6 with opposite helix directions so as to terminate freely in both ends.

The blocking device illustrated functions in such a way that by rotational movement of the race ring 5 in the direction shown by the arrow 8, the engagement be¬ tween the helical spring 13 and the race ring 5 or the intermediate ring 12 will be loosened, so that the race 1 is allowed to turn in this direction relative to the race 10. On the other hand, no rotation of the race 11 in the direction shown by the arrow 8 relative to the

O PI IPO , race 2 will be allowed, since such rotational movement will be prevented as a result of the fact that the enga¬ gement between the helical spring 14 and the intermediate ring 12 and the race ring 6 will be tightened. In case of rotational movement of the race ring 5 in the direction shown by the arrow 9, however, the en¬ gagement between the helical spring 13, and the race ring 5 and the intermediate ring 12 will be tightened, so that the race ring 5 and, thereby, the race 1 will not be allowed to turn in this direction relative to the race 10. ^• herefore, by this rotational movement of the race ring 5, the intermediate ring 12 will be carried along and also turned in the direction shown by the arrow 9. Thereby, the engagement between the helical spring 14 and the intermediate ring 12 or the race ring 6 will be loosened, so as to allow the race 11 to turn in the di¬ rection shown by the arrow 9 relative to the race 2.

By use of a thrust bearing device of the construc¬ tion shown as a blade suspension bearing in an axial flow fan, the race ring 5 with the race 1 will be con¬ nected with the blade, whereas the race ring 6 with the race 2 will be retained relative to a bearing bore in the wheel rim of the fan wheel. During rotation of the fan with a given blade pitch setting, the pulses suppli- ed to the usually servo-controlled blade pitch adjusting mechanism may cause small oscillating rotational movements of the fan blades, and this oscillating movement of each blade will be transferred to the race 1 of the thrust bearing device connected with the blade. Since the race 1 is only allowed to turn in the direction shown by the arrow 8 relative to the race 10, whereas the race 11 is only allowed to turn in the direction shown by the arrow 9 relative to the race 2, the rollers 3 and 4 in the two series-coupled bearings will be alternatively active for one and the other direction of revolution in this oscil¬ lating movement, and for each rotational movement in each of the two bearings, the rollers will be displaced to local engagement with new points of contact on each

OMP WIP of the races in question, whereby the risk for blocking relative to the races as a result of brinelling is sub¬ stantially avoided.

Figs. 2 and 3 are an axial sectional view and a side view, respectively, of a possible practical embodiment of a thrust bearing device of the embodiment illustrated in principle -in Fig. 1. Since the structural arrangement is, in principle, the same as in Fig. 1, elements corres¬ ponding to those shown in Fig. 1 have been designated by the same references. In addition thereto, parts of a wheel rim for a fan wheel is shown at 15, in which a bore 16 is formed for a blade shaft 17 connected with a con¬ trol arm, not shown, which is connected with a blade pitch adjusting mechanism of a design known per se. On the blade shaft 17 a flange 18 is secured, and the thrust bearing device is arranged between the surfaces facing each other of this flange 18 and the bottom of a cut-out 19 at the internal side of the wheel rim 15 around the bore 16. Contrary to the principal arrangement illustrated in Fig. 1, the relatively immovable races 10 and 11 in each of the two series-coupled bearings in Fig. 2 are formed on each of two separate race rings 20 and 21, re¬ spectively, arranged on opposite sides of an intermediate ring 22, which is connected with two helical springs 13 and 14 constituting together the spring coupling acting as a blocking device. In the embodiment shown, these he¬ lical springs do not directly engage each of the two re¬ latively movable race rings 5 and 6, but enclose each of two bearing casings 23 and 24, which are firmly connect¬ ed with the race ring 5 and the wheel rim 15 and with the race ring 6 and the flange 18 secured on the blade shaft, respectively.

Fig. 3 is an external view of the thrust .bearing device in Fig. 2. The two helical springs 13 and 14 en¬ closing each of the bearing casings 23 and 24 may, as shown, be formed integrally from strip-shaped material, such as steel plate, by stamping and subsequent rolling and hardening, whereby to obtain in addition a favour¬ able closing of the bearing device against dust and dirt. By this design, the individual spring windings will, on the major part of their periferal length be pa- rallel to a radial plane, subsequent spring windings be¬ ing connected by oblique intermediate pieces. In the fi¬ gure, helical..springs 13 and 14 are shown, each having two windings, but of course nothing would prevent use of helical springs with a greater number of windings suitable for the axial dimension of the thrust bearing device.

However, a particularly simple and cheap embodiment is obtained, if instead of the special springs shown in Fig. 3, standard helical springs 13' and 14 ' of flat or round spring wire having elliptical or circular cross- section are used, as shown in Figs. 4 and 5, and arran¬ ged without any firm connection, whereby the two race rings 20 and 21 may be secured in a common bearing casing 24', enclosed by both helical springs 13' and 14'. In Figs. 6 to 9, various embodiments of the thrust bearing device according to the invention are illustrat¬ ed in use as a blade suspension bearing in the fan wheel of an axial flow fan, the wheel rim thereof being shown at 25, whereas 26 designates a fan blade which in a manner not illustrated is firmly connected with a blade flange 27 positioned in a cut-out 28 at the external side of the wheel rim 25. In a manner not illustrated, a flange portion 29 of a control member for adjusting the blade pitch is secured to the blade flange 27. In this case, contrary to the embodiment illustrated in Figs. 4 and 5, no blade shaft is connected with the fan blade 26. In the embodiment shown in Figs. 6 and 7, modifica¬ tions of the embodiment shown in Figs. 4 and 5 have been used as a blade suspension bearing, the thrust bearing device comprising two coaxial bearings having the same diameter, which are series-coupled with respect to their loading forces. In Fig. 6, the mutually movable races of the bearing device are constituted by the radial faces facing each other of two race rings 34 and 35, one of which is firmly connected with the wheel rJLm 25, whereas the other is connected with the flange portion 29. The relatively immovable races are formed by opposite radial surfaces on an intermediate race ring 36 common to the two bearings . In the same manner as in the embodiment shown in Figs. • 4 and 5, the blocking device is constitut¬ ed by a spring coupling comprising two helical springs, which are designated by 37 and 38 in Fig. 6, but are ar- ranged, in this case, on the internal side of the race rings 34, 36 and 36, 35, respectively, whereby a bushing 39 and 40, respectively, has been interposed between each of the helical springs 37 and 38 and each of the race rings 34, 36 and 36, 35, respectively, covered thereby, said bushings being slit in a manner not illustrated in the axial direction of the bearing for transferring the spring pressure from the helical springs 37 and 38 to the race rings. As shown in the figure at 39a, 39b and 40a, 40b, two axially aligned bushings must be used for each bearing for obtaining an independent tightening function around the movable race ring 34 and 35, respectively, and the immovable race ring 36 of the bearing in question.

Since the helical springs 37 and 38 are arranged with different helix directions in the same manner as in the embodiments shown, in Figs. 3 to 5, the embodiment shown in Fig. 6 will function, in principle, in the same manner as described in the foregoing for the embodiment in Fig. 3, bearing in mind only that in case of internal- ly arranged helical springs 37 and 38, the engagement be¬ tween each of such springs and the corresponding race rings will be tightened or loosened, respectively, when the rotational movement takes place in the opposite di¬ rection and the same direction, respectively, relative to the helix direction of the helical spring.

In the embodiment shown in Fig. 7, in which parts corresponding to those shown in Fig. 6 are designated by the same references, the blocking device is designed in

-ξ/OfEATT OMPI the same manner with two helical springs, of which, how¬ ever, one 41 is arranged on the internal side of the race rings 34 and 36, whereas the other 42 is arranged on the external side of the race rings 36 and 35. In this case, contrary to the embodiments shown in Figs. 3 to 6, the two helical springs 41 and 42 should be arranged with the same helix-direction.

For blade^" suspensions of the kind shown in Figs . 6 and 7, the simplest design will be obtained with the em- bodiment shown in Fig. 6, in which helical springs having a somewhat smaller diameter may be used. On the other hand, in the embodiment shown in Fig. 7, an improved en¬ gagement of the lower race ring 35 of the relatively mov¬ able race rings relative to the flange portion, here de- signated by 31, of the control member will be obtained without any requirement of a raised rim portion 30 on the flange portion as engagement for the race ring 35, such as shown in Fig. 6.

Whereas the embodiment of the thrust bearing device described in the foregoing will have a relatively great dimension in the .axial direction due to the use of two bearings having the same diameter, which may be undesired in applications, in which only limited space will be available for the bearing, such as may be the case for blade suspensions of the kind shown in Figs. 6 and 7, Fig..8 shows an embodiment, in which a somewhat smaller height and thereby a smaller demand of space in the axial direction has been obtained by using two coaxial bearings having different diameters, said bearings being series- coupled with respect to their loading forces. In this case, the relatively movable races are formed on the ra¬ dial -surfaces facing each other of a race ring 43 firmly connected with the wheel rim 25, and a race ring 44 se¬ cured in the flange portion designated in this embodiment by 32. In the two bearings, the relatively immovable races are formed on the radial surfaces of two separate race rings 45 and 46, respectively, facing the race rings 43 and 44, said separate race rings being mutually

( OMPI connected and, thereby, prevented from relative movement in this case by means of a separate intermediate member 47, since they must be movable relative to the wheel rim 25 as well as the flange portion 32. In this case, the spring coupling acting as a blocking device is construct¬ ed in the same way as in the embodiment shown in Fig. 7 with two helical springs, one of which 48 is arranged on the internal side of the race rings 43 and 45 in engage¬ ment with axial slit bushings 50, whereas the other helical spring 49 is arranged on the external side of the race rings 46 and 44 -in engagement with axial slit bushings 51.

For use in blade suspensions of the kind shown in Figs. 6 to 8, Fig. 9 shows an alternative embodiment of the thrust bearing device employing two series-coupled bearings having different diameters. The race rings firm¬ ly connected with the wheel rim 25 and the flange portion designated in this case by 33, respectively, are designa¬ ted by 52 and 53, respectively, whereas the relatively immovable races in the same manner as in the embodiment shown in Fig. 8 are formed by radial faces on two sepa¬ rate race rings 54 and 55, respectively. In the same man¬ ner as in the embodiment shown in Fig. 8, the difference between the bearing diameters is such that the race ring 54 for the bearing connected with the wheel rim 25 com¬ pletely encircles the race ring 55 for the bearing con¬ nected with the flange portion 33 in substantially the same radial plane.

In the embodiment shown in Fig. 9, the blocking de- vice functioning to prevent the relatively immovable ra¬ ces defined by the race rings 54 and 55 for each of the two bearings from rotating in one and the other direction of revolution, respectively, relative to the opposed race 52 and 53, respectively, is constituted by a coupling member 56 firmly connected with the race rings 54 and 55, said coupling member being restricted to turn in a pre¬ scribed direction of revolution only, relative to the race rings 52 and 53, since it is positioned radially

^*flϊRE

OMPI

Λ. WIPO < between the two race rings in the same manner as the in¬ termediate member 47 shown in Fig. 8. In the embodiment shown in Fig. 9, this is obtained in that the coupling member 56 may be coupled to the wheel rim 25 and the flange portion 33, respectively, and thereby to the race rings 52 and 53, respectively, through a roller clutch. Between each side of a peripheral collar 57 having a wedge-shaped cross-section on the coupling member 56 and an opposed external set of protrusions 58 on the flange portion 33 and an opposed internal set of protru¬ sions 59 on a ring 60 firmly connected with the wheel rim 25, respectively, two sets of conical rolls 61 and 62, respectively, are arranged so as to make up two roller clutches. Thereby, as shown in Fig. 10, the coupling member 56 will be restricted to rotational movement in the di¬ rection of revolution shown by an arrow 63 only, rela¬ tive to the ring 60 connected with the wheel rim 25 as well as the flange portion 33. By movement of the flange portion 33 connected with the blade 26 in the same di¬ rection as the arrow 63, the coupling member 56 will be carried along, whereby the race ring 54 will perform a rotational movement relative to the race ring 52. By rotational movement of the flange portion 33 in the op- posite direction against the arrow 63, the flange portion 33 will, on the contrary, perform a rotational movement relative to the coupling member 56, whereas, on the other hand, the coupling member will be retained against rota¬ tion relative to the ring 60. Thereby, the race ring 53 will turn relative to the race ring 55.

As shown in Fig. 9, it is not necessary in a thrust bearing device according to the invention to use rollers of the same kind in the series-coupled bearings. For example, nothing could prevent the use of balls 64 in one bearing and cylindrical rollers 65 in the other bear¬ ing, or the use of any suitable form for rollers in each of the two bearings.

OMPI WIPO Industrial applicability

Even if the foregoing embodiments of the thrust bearing device according to the invention are mainly de¬ scribed with reference to their use as blade suspension bearing in axial flow fans, these bearing devices may also be used in other kinds of axially loaded thrust bear¬ ings in cases,in which a risk will otherwise prevail for deterioration ^"of the races as a result of the fact that only a limited portion thereof is utilized in normal ope- ration. As examples of such fields of application, refer¬ ence could particularly be made to the thrust bearings mentioned in the foregoing used in the front wheel sus¬ pension of vehicles, such as automobiles, and thrust bearings of the kind utilized in the rudder suspension in ships, with the considerable advantage that continu¬ ous displacement of the rollers relative to the races takes place steplessly for any rotational movement and independent of the magnitude thereof.

OMPI

Claims

P A T E N T C L A I M S

1. A thrust bearing device, particularly for taking up oscillating rotational movements of two relatively movable coaxial roller races {1, 2) positioned in paral¬ lel planes and axially loaded relative to each other, said races constituting one of the races of each of two coaxial thrust bearings coupled in series with respect to their loading forces, in which bearings the two oppo¬ site races (10, 11) are immovable relative to each other and are prevented by a blocking device from rotating in one and the other direction of revolution, respectively, relative to one and the other of said relatively movable races (1, 2) , characterized in that said blocking device is constructed to allow substantially stepless relative rotational movement between said relatively immovable races (10, 11) and one or the other of said relatively movable races (1, 2) without any axial displacement of the latter relative to each other.

2. A thrust bearing device as claimed in claim 1, characterized in that said blocking device is constitut- ed by a spring coupling comprising two helical springs

(13, 14; 13', 14'; 37, 38; 41, 42; 48, 49) , each of which is arranged for spring action against two race rings (5, 12, 12, 6; 5, 20, 21, 6; 34, 36, 36, 35; 43, 45, 46, 44; 52, 54, 55, 53) belonging to the same bearing, each of said springs terminating freely at least in one end.

3. A thrust bearing device as claimed in claim 2, in which said race rings have the same diameter for the two bearings, characterized in that both of said helical springs (13, 14; 13', 14'; 37, 38) are arranged on the same side of said race rings seen in the radial direction and with opposite helix directions relative to one another.

4. A thrust bearing device as claimed in claim 3, characterized in that the two helical springs (13, 14) are formed integrally from strip-shaped material (Figs. 2-3).

5. A thrust bearing device as claimed in claim 4 , characterized in that said relatively immovable races (10 , 11) are formed on two individual race rings (20, 21) each belonging to one of said bearings, said race rings being arranged on opposite sides of an intermediate ring (22) which is connected with said integral helical springs (13, 14) .

6. A thrust bearing device as claimed in claim 1 or 2, characterized in that said bearings have different diameters and "partly overlap each other in the axial di¬ rection.

7. A thrust bearing device as claimed in claim 3 or in claims 2 and 6, characterized in that one helical spring (41, 48) is arranged inside the two race rings (34, 36; 43, 45) belonging to one bearing, whereas the other helical spring (42, 49) is arranged outside the two race rings (36, 35; 46, 44) belonging to the other bearing, the two helical springs having the same helix direction.

8. A thrust bearing device as claimed in claim 3 or claim 7, characterized in that said helical springs are manufactured from spring wire engaging the race rings belonging to each bearing without any firm connection therewith.

9. A thrust bearing device as claimed in any of claims 2-5, 7 or 8, characterized in that an axial slit bushing (39, 40; 50, 51) is interposed between each helical spring (37, 38; 41, 42; 48, 49) and each of the race rings influenced thereby ih engagement with said race ring.

10. A thrust bearing device as claimed in claim 9, characterized in that said bushing (39, 40; 50, 51) is divided into two parts in the axial direction.

10. A thrust bearing device as claimed in claim 1 or 6, characterized in that the race rings (54, 55) for the relatively immovable races are coupled through a coupling member, which is restricted to rotation in a prescribed direction of revolution (63) relative to each of said relative movable races (52, 53) .

11. A thrust bearing device as claimed in claim 10, characterized in that said coupling member (56) may be coupled with one or the other of said relatively movable races (52, 53) in each bearing through a roller clutch (58, 61; 59, 62) .