EP0918958A1

EP0918958A1 - A method for immobilizing balancing means in an autobalancing device and such an autobalancing unit

Info

Publication number: EP0918958A1
Application number: EP97937923A
Authority: EP
Inventors: Jonas Nilsag Rd; Peter Kinde; Anders HÄGGLUND; Magnus Lindholm
Original assignee: SKF AB
Current assignee: SKF AB
Priority date: 1996-08-27
Filing date: 1997-08-27
Publication date: 1999-06-02
Also published as: AU4037197A; JP2000501488A; CN1072785C; CN1228829A; WO1998009096A1; SE9603105D0; DE19781954T1

Abstract

A method for immobilizing balancing means in an autobalancing unit comprising an encased annular track (11) mounted to a rotary system and having balancing means (3) in form of rolling bodies freely moveable along said track for compensating imbalance in the rotary system, and intended for intentionally during rotation of the rotary system to arrest the balancing means (3) in their momentary positions after the balancing function has been established, comprising the steps of arranging at a position spaced apart from said track (11) a bistable lid (9; 17; 18), having a first distinct position (17a, 18a) in which it is situated entirely outside the space (4) housing the rolling bodies (3), and a second distinct position (17b, 18b), in which it is arranged to engage the rolling bodies with an arresting force keeping the balls immobilized, and applying a triggering force to said bistable lid, for moving it from its first to its second position, or applying a force (19) on the autobalancing unit for causing on the rolling bodies a wedging effect, clamping said rolling bodies (3) against at least the race track (11) of the unit.

Description

A METHOD FOR IMMOBILIZING BALANCING MEANS LN AN

AUTOBALANCING DEVICE AND SUCH AN AUTOBALANCING UNIT

The present invention refers to a method for accomplishing automatic balancing in an autobalancing device of the type used for controlling vibration imparted on different types of rotary systems following imbalance in said systems, and comprising an encased annular track mounted to the rotary system and having balancing means freely moveable along said track for compensating imbalance in the rotary system, primarily of the well-known type having a number of rolling bodies freely movable in said track, which rolling bodies during rotation of the system automatically will find their appropriate angular positions along the path for automatically outbalancing the imbalance and allowing the system to operate at a substantially reduced vibration level, to compensate for the inherent imbalance of the system. The invention further refers to such autobal^¬ ancing units.

The balancing function with such an autobalancing device is achieved at certain rotational speed interval or intervals and when the speed is later on changed, or when disturbances_, such as resonance phenomena or ignition frequencies appear, the rolling bodies might again begin to "float" around in their path in the device, which thereby looses its outbalanced state.

Many applications wherein such autobalancing devices are used will not alter their inherent imbalance properties from one time to another, and therefore they require merely that the autobalancing device provides an outbalancing of the rotary system when the system is started up for the first time. The rolling bodies in such an autobalancing system thus will take up the same positions every time a state of balance is reached after the rotary system has been started up again, and for this reason it would be advantageous to be able in a simple manner to maintain the positions of the rolling bodies in their balancing positions also when the rotary systems is accelerated, slowed down or even brought to a complete stop, thus that the system is already in balance the next time the rotary system is started up from stillstand. In this

CONFIRMATION COPY manner it would be possible to use the effects of the autobalancing device over the complete speed range of the rotary system to which it is connected.

At a conventional method for manually balancing a car wheel, the wheel is mounted on a spindle in a measuring machine, the spindle is rotated to let the machine indicate the imbalance of the wheel, balancing weights are thereupon manually fitted to the wheel rim in accordance with the values obtained at the measurements, the spindle with the wheel with balancing weights manually affixed thereto is thereupon again rotated and if necessary further weights are attached to the wheel rim, until the machine indicates an acceptable degree of imbalance. Thereupon the wheel is removed from the spindle and is mounted on the vehicle to which it shall then be fitted. This procedure requires that the rotating system (the wheel) is balanced in a place, where it shall not operate, and the steps for minimizing the imbalance in the wheel itself are manual. The result is a car wheel which has been subjected to a balancing operation in the condition the wheel has at the time of balancing. This method otherwise can be considered to lock the balancing bodies in positions, where they provide a balancing effect, but it also must be observed that this is correct only under the very conditions at hand at the moment of balancing. Any disturbance during removal of the wheel from the measuring machine spindle, transfer of it to the car and the mounting it on the car means that the balanced system can be subjected to new uncontrolled imbalance and/or misalignment, and the conditions of the components of the car to which the wheel is mounted is not taken in account at the balancing. As long as the wheel is not subjected to impacts or wear which alter the weight distribution therein, this type of balancing action can be appropriate, but uneven wear of the tread surface of the wheel or impacts causing the wheel to be warped can mean that the rotary system - the wheel - looses its balanced condition. Such a permanent, manual outbalancing of a rotary system therefore is quite unacceptable at fast rotating systems subjected to wear e.g. in grinding machine spindles, or systems having large inherent vibration amplitudes, such as e.g. washing machine drums. US-A-4,060,009 discloses an autobalancing unit wherein an adhesive is positioned in the annular cavity housing balancing balls. The adhesive is activated by temporarily placing an electric heating coil externally to the system in order to permanently lock the balls in balancing position, to let the rotating system to which the unit is attached be per- manently balanced. Such an arrangement might give a satisfactorily result, when the balancing shall be non-reversable, but the temporary positioning of the electric coil about the unit during rotation and removal thereof after activation of the adhesive is a time- consuming and complex work.

US-A-3,433,534 discloses, i.a. a mechanical means for locking the balancing bodies in a retainer forming part of an automatic balancer in balancing positions, said means being a segmented spring-urged clamping member, wedging between the balancing bodies. The device is also equipped with means for releasing the rolling bodies for rebalancing, if desired, e.g. in form of a solenoid. This device allows a reversible arresting of the bal- ancing bodies, but the plurality of mechanical elements makes it bulky and complicated.

The purpose of the present invention is to propose methods performed at autobalancing units whereby it is ascertained that the autobalancing function in a reversible or non-reversible manner is maintained over the entire speed range and which is quite insensitive to different types of disturbances, and this is achieved in a simple and efficient manner as defined in the accompanying claims.

Hereinafter the invention will be described more in detail with reference to the accompanying drawings, showing schematically in

Fig. 1 a diagrammatic side illustration over an autobalancing unit with the rolling bodies thereof distributed randomly in the position occupied prior to balancing.

Fig. 2 is a corresponding view showing the rolling bodies gathered in a sector of the race track in their balancing positions. Fig. 3 shows in cross section an autobalancing device provided with first embodiments of mechanical means for automatically immobilizing the rolling bodies at a certain rotational speed in form of bistable members.

Figs. 4 and 5 show in partial cross sectional views further embodiments of bistable members for arresting rolling bodies.

Fig. 6 illustrates an embodiment wherein the autobalancing unit may be subjected to an external force or impact deforming a portion of the very device for immobilizing the rolling bodies.

Fig. 7 and 8 illustrate schematically in partial views further embodiments of immobilizing the rolling bodies of an autobalancing unit wherein a conical socket is used preferably in combination with pyrotechnics.

Fig. 9 shows in a partial view an embodiment for relieving the force arresting the rolling bodies, for making the arrangement reversible,

Figs. 10 and 1 1 show cross sections of a housing and a conical socket for an autobalancing unit adapted for use of pyrotechnics for initiating the immobilization function of the rolling bodies, and

Fig. 12 shows in a partial and more detailed view of the bistable lid member shown in

Fig. 4.

In Fig. 1 is schematically illustrated in a side view, an autobalancing unit, intended to be connected concentric to a rotary shaft or the like, which shall be outbalanced, and comprising an inner ring 1 , an outer race ring 2 positioned about the inner ring 1 and concentric thereabout and a number of rolling bodies 3, preferably balls, said rolling bodies being of such a number that they occupy only a part of the volume contained between the two rings 1 and 2. Although not shown in this figure the space 4 between the rings 1 ,2 is closed off laterally by means of not shown end plates, and the free volume between rings and end plates, not occupied by the rolling bodies 3 is sometimes filled with a liquid or semi-liquid medium, e.g. oil having the main purposes of exerting a dampening, pulling-along and lubricating effect on the rolling bodies. The unit in this figure is shown in imbalance condition, whereby an imagined out-off-balance effect is illustrated in the upper right hand quadrant of the outer race ring at 5, and wherein the system is rotating at a speed sufficient for achieving balancing, but before the rolling bodies have begun moving towards their positions in which they out-balance the out-off-balance 5. The rolling bodies 3 here are situated in spaced apart random positions along the outer race ring and as illustrated for the lowermost ball 3 as shown in Fig. 1, these rolling bodies are subjected to a parallelogram of forces due to the out-off-balance 5, as in imbalance position the geometrical centre 6 and the centre of gravity 7 of the system do not coincide. For this reason the centrifugal force Fc and the force normal to the race track Fn together give a resulting force Fr acting on the balls, and after the system has accelerated to a rotational speed, at which balancing occurs the balls 3 have gathered at positions opposite to the position for the out-of-balance effect 5, and thereby the disturbing out-off-balance 5 is compensated, and the centrifugal force Fc acting on the rolling body and the normal force Fn acting perpendicularly towards the race track are equal and directed in opposite directions and through the centre of gravity MC and the geometrical centre GC, which now coincide. Therefore there is no resulting force causing imbalance when the system is running.

The out-off-balance symbol 5 in the drawing is illustrated as a rather large area, representing a comparatively big mass, and, according to Fig. 2, the rolling bodies 3 in balanced position are positioned close to each other over a short portion of the race track. If the size of the out-off-balance 5 and/or the distance between the position for 5 and the geometrical centre GC was smaller, then the rolling bodies of course should be more spaced apart but still positioned opposed to the position for the out-off-balance 5.

The rotational speed at which the autobalancing effect occurs is occasionally over- critical, but the rolling bodies are normally not stationary in the balancing positions, when the rotational speed is lowered to the normal operating speed for the machinery equipped with the autobalancing device, and different types of disturbances, such as blows, altered weight distribution (e g due to wear) etcetera, might cause the rolling bodies to leave their balancing positions, thereby not permitting that the machinery will operate in balanced condition at operational speeds other than at balancing speed

It now therefore is proposed in accordance with the present invention a method in an autobalancing unit of the type used for controlling vibration imparted on different types of rotary systems following imbalance in said systems, and comprising an encased annular track mounted to the rotary system and having balancing means, preferably a number of rolling bodies freely moveable along said track for compensating imbalance in the rotary system, whereby the rolling bodies intentionally are arrested in their momentary positions duπng rotation of the rotary system when the balancing function has been established

In this manner it is possible to ascertain that a rotary system once balanced will maintain its balanced condition independent of the rotational speed of the rotary system and without being influenced by external disturbances

For many applications of autobalancing it is also of interest to arrest the rolling bodies in their momentary positions in a reversible manner, l e thus that it is possible later on to cause the rolling bodies to be re-arranged if the conditions of imbalance have been changed, whereas it in other circumstances can be preferable to arrest the rolling bodies in a balanced position, in a non-reversible manner

The aim is to bring about such an instantaneous arresting of the rolling bodies duπng the time the rotary system is rotating and as soon as a state of balance has been achieved In a first basic embodiment illustrated schematically in Figs 3-5, the arresting function is obtained by using a bistable arresting member having two distinct positions, a first one in which the rolling bodies are free to move in the track provided in the autobalancing unit, and a second position in which the bistable membei exerts a retaining force on the rolling bodies A first embodiment of this is illustrated in Fig. 3 wherein a spring-like member 9 fitted in the autobalancing unit at a position 10 spaced apart from the race track 1 1 of the unit which comprises an inner ring 12 and an outer race ring 13 forming an integral unit via the intermediary of one gable side 14 , wherein is formed an annular space 4 housing a number of rolling bodies 3. The other gable side of the unit is closed off by means of an end plate 15 fitted thereto in a appropriate, leak-proof manner.

As shown in the upper half of Fig. 3, the mechanical bistable, spring-like member 9, can be held in inactive position by a catch 16, which can be brought to release the spring-like member 9, when triggered e.g. by an external impulse or the like. When positioned in a manner as intimated in this figure, the arrangement also can be chosen in such a manner that the member 9, will automatically be triggered and move to active position by influence of the centrifugal force caused by rotation at over-critical speed.

Fig. 4 illustrates schematically a preferred embodiment of a bistable arresting means, which in this case is designed as a gable lid 17. The bistable lid 17 has two distinct positions, i.e. a first one 17a, illustrated with continuous lines in Fig. 5, and a second distinct position 17b, shown in dash lines. When the bistable lid 17 is in its first position 17a, the rolling bodies are not in engagement therewith, and are therefore freely movable along their track, but following a trigging force pushing the centre of the lid member 17 inwards to the second distinct position 17b, the central portion thereof engages the rolling bodies 3, thereby locking the rolling bodies by clamping them in their current positions against the race track and possibly also against the gable 14 of the unit opposed to the position for the lid member 17. The lid member 17 in this embodiment can serve as the very outer gable of the autobalancing unit, but it is also possible to have this arresting, bistable lid member 17, situated inside a not shown gable of the unit.

In Fig. 12 is shown schematically how the bistable lid 17 can be mounted in proper recesses in the outer race ring 13 and the inner ring 12 and how the lid member 17 on the side surface facing the rolling bodies 3, is preferably equipped with a flexible lining, 18, such as rubber, whereby the force required for arresting the rolling bodies, i.e the force of the bistable lid acting against the rolling bodies can be reduced essentially For this purpose it also is possible to provide the opposed gable (not shown in this figure) with a corresponding internal lining for further reducing the force required

In Fig 5 is schematically shown another embodiment of a bistable lid member 19, which in this case extends only over a part of the space between the rings 12 and 13 In this case the function of the bistable lid is similar to that according to Fig 4, but it is of course not possible to let this type of bistable lid 18 form the outer gable of the unit, as this then would not be encased Also in this case the bistable lid 18 and preferably also the opposed gable are preferably provided with flexible linings reducing the required retaining force, at least in the areas which will engage the rolling bodies 3 duπng arresting

Figs 6-1 1 show another type of embodiments for achieving arresting of the rolling bodies in desired positions, 1 e in positions when balancing effect is obtained for the rotary system.

This type of arresting is concerned with methods wherein a force is applied substantially axially to the autobalancing unit, said force being used to causing the race track and/or a side face of the housing encasing the rolling bodies such as shown in Fig 6 to be deformed Here it is illustrated how, in the upper half of the figure, a force 19 is applied e g to the side gable 15 of the housing encapsulating the rolling bodies 3, when these have reached a state of balance, which force - as shown in the lower half of the figure - causes the side gable 15 to be deformed 20, thus that it prevents further movement of the rolling bodies For this purpose the side plate can preferably be provided with some sort of pre-shaped indications of deformation for allowing a safe arresting of the rolling bodies

Fig 7 shows in a schematical partial cross sectional view a portion of an autobalancing unit, wherein the rolling bodies 3 can be pressed against the race ring 13, thereby becoming arrested by means of a conical socket 21 , which is pushed in axially between the rolling bodies and the inner ring 12. In this embodiment the conical socket 21 is caused to move axially by means of a pyrotechnic charge 22. The housing for this embodiment is further illustrated in Fig. 10, whereas the conical socket 21 is shown in bigger scale in a partial cross section in Fig. 1 1. Also the arrangement shown in Fig. 8 incorporates a conical socket 21, arranged to cooperate in a manner similar as at the embodiment according to Fig. 7 with the rolling bodies 3 and the race ring 13. In this case the socket 21 has a peripheral groove 21a, wherein is inserted the end of a spring-formed member 23 arranged to keep the conical socket 21 in position. Also in this case the conical socket is preferably moved to arresting position by means of a pyrotechnic charge (not shown), which can be adapted thus that it causes an instantaneous arresting, with only fractions of a second from the ignition until the conical socket 21 has been driven up to arrest the rolling bodies.

In this embodiment the spring-like member 23 could also serve as the gable of the housing.

In Fig. 9 is shown in a view corresponding to Fig. 8 a simple arrangement for making the embodiment according to Fig. 8 reversible. This is obtained by providing an air duct 24 in a wall of the housing of the unit. When the pyrotechnic charge is exploded to drive in the conical socket air can escape through this air duct 24 for preventing that a high pressure is built up in the space 4 housing the rolling bodies 3, and when the unit shall be subjected to a re-balancing, the air duct 24 can be used for introduction of pressurized air or the like, causing the spring-like member 23 to bulge outwards, thereby retracting the conical socket 21 from its position locking the rolling bodies 3 in balanced position. It is preferable if the air duct 24 is arranged and designed in such a manner as to allow a certain delay between the commencement of the introduction or draining of air or the like from the interior of the housing and until the conical socket has been displaced from one of its positions to the other.

The same is valid also for the variants using bistable means according to Figs. 3 to 5. In Fig 10 as mentioned above, is shown more in detail a housing 25 for an autobalancing unit using a pyrotechnic charge for trigging a conical socket for wedging the rolling bodies against the race track in the race ring 13 In this embodiment, substantially corresponding to the schematically shown embodiment according to Fig 7, is shown an inner ring 12, an outer race ring 13, which are made in one piece via the intermediary of a fixed gable wall 14 The housing has an annular, circumferential recess 26, preferably provided in the fixed gable 14, and intended to receive an annular pyrotechnic charge (not shown) An opening 27 is provided through the fixed gable 14 and opening in the recess 26 This opening 27 is intended for reaching the pyrotechnic charge, when this is positioned in the recess in order to cause the charge to explode for driving up the conical socket

The conical socket 21 , is shown more in detail in Fig 1 1 , whereby only half the socket is shown in cross-section As can be seen, this conical socket 21 has a tapering outer envelope surface 28, and at one side a projecting πm 29, which is intended to fit into the recess 26 in the housing, thereby acting as a piston, which is driven axially outwards when the pyrotechnic charge is caused to explode

The invention is not limited to the embodiments schematically shown in the drawings and described with reference thereto but modifications and variants are conceivable within the scope of the appended claims

Claims

1. A method in an autobalancing unit of the type used for controlling vibration imparted on different types of rotary systems following imbalance in said systems, and comprising an encased annular track (11) mounted to the rotary system and having balancing means (3) in form of rolling bodies freely moveable along said track for compensating imbalance in the rotary system, and intended for intentionally during rotation of the rotary system to arrest the balancing means (3) in their momentary positions after the balancing function has been established, characterized in arranging at a position spaced apart from said track (11) a bistable lid (9; 17; 18), having a first distinct position (17a, 18a) in which it is situated entirely outside the space (4) housing the rolling bodies (3), and a second distinct position (17b, 18b), in which it is arranged to engage the rolling bodies with an arresting force keeping the balls immobilized, and applying a triggering force to said bistable lid, for moving it from its first to its second position.

2. A method as claimed in claim 1 , characterized in using a toroidally shaped bistable lid (17).

3. A method as claimed in claim 1, characterized in using a conically shaped ring member (18) as said bistable lid.

4. A method as claimed in anyone of claims 1 to 3, characterized in lining the surface of the bistable lid (17,18), which in its second distinct position

(17b, 18b) will be in an arresting contact with the rolling bodies, with a flexible material (17c) for reducing the force required for arresting the rolling bodies.

5. A method as claimed in claim 4, wherein the bistable lid (17, 18) is positioned axially outside the space (4) housing the rolling bodies (3), characterized in providing a gable (14) of the autobalancing unit opposed to said bistable lid (17, 18) with an internal lining of a flexible material, for further reducing the force required for arresting the rolling bodies.

6. A method as claimed in anyone of claims 1 to 5, wherein the encased space (4) for the rolling bodies have at least one sealingly arranged wall, characterized in providing for air ventilation (24) through said wall of the encased space (4) for the rolling bodies (3) for permitting airflow at displacement of said bistable lid (9,16,17).

7. A method in an autobalancing unit of the type used for controlling vibration imparted on different types of rotary systems following imbalance in said systems, and comprising an encased annular track (4) mounted to the rotary system and having balancing means (3) in form of rolling bodies freely moveable along said track for compensating imbalance in the rotary system, and intended for intentionally during rotation of the rotary system arresting the balancing means (3) manner in their momentary positions when the balancing function has been established, characterized in applying a force (19) on the autobalancing unit for causing on the rolling bodies a wedging effect, clamping said rolling bodies (3) against at least the race track (11) of the unit.

8. A method as claimed in claim 7, characterized in applying a force (19) against a gable lid (15) of the autobalancing unit, thereby causing a deformation (20) of said gable lid (15) for wedging the rolling bodies (3) against the race track (11) and preferably against the opposed gable (14) of the unit. 13

9. A method as claimed in claim 8, characterized in using a conical socket (21) positioned between the rolling bodies (3) and the inner ring (12) of the unit, and displacing said coiiical socket axially, to clamp the rolling bodies (3) against the race track (11) of the outer race ring (13),

10. A method as claimed in claim 9, characterized in using together with said conical socket (21) a spring-formed member (23), connected thereto and maintaining the said socket in position.

11. A method as claimed in claim 10, cha acterized in using the said spring-formed member (23) as a lid member sealing off the side of the housing remote from the fixed gable (14).

12. A method as claimed in anyone of claims 7 to 11, ch ar ac terized i n providing for air ventilation (24) through a wall of the encased space (4) for the rolling bodies (3) for permitting air flow at displacement of said conical socket (21).

1 . A method as claimed in anyone of claims 7 to 12, char cterized in causing said force (19) for clamping the rolling bodies in position, by exploding a pyrotechnic charge (22).

14. An autobalancing unit of the type used for controlling vibration imparted on different types of rotary systems following imbalance in said systems, and comprising an encased space (4) with an annular track (11) mounted to the rotary system and having balancing means (3) in form of rolling bodies freely moveable along said track for compensating imbalance in the rotary system, and wherein the rolling bodies are arranged rotation of the rotary system to be arrested in their momentary positions when the balancing function has been established, char c erized therein that a bistable means (9, 17, 18) having a first position (171, 18a) for permitang the rolling bodies (3) to move freely in their annular track (11) and a second position (17b,

18b) pressing the rolling bodies (3) against at least one fixed object (11, 14), is provided in the housing of the autobalancing unit.

15. An autobalancing unit of the type used for controlling vibration imparted on different types of rotary systems following imbalance in said systems, and comprising an encased space (4) with an annular track (11) mounted to the rotary system and having balancing means (3) in form of rolling bodies freely moveable along said track for compensating imbalance in the rotary system, and wherein the rolling bodies are arranged rotation of the rotary system to be arrested in their momentary positions when the balancing function has been established, characterized therein, that the unit is provided with means (26) for receiving a pyrotechnic charge (22) arranged to be exploded for displacing a component (15; 21) forming part of the autobalancing unit for causing the rolling bodies to be arrested in positions by a wedging force.