GB1604862A

GB1604862A - Bearing assemblies incorporating sensing devices

Info

Publication number: GB1604862A
Application number: GB2358/81A
Authority: GB
Original assignee: Ransome Hoffmann Pollard Ltd
Current assignee: Pilgrim House Group Ltd
Priority date: 1978-05-26
Filing date: 1978-05-26
Publication date: 1981-12-16

Description

(54) IMPROVEMENTS IN OR RELATING TO BEARING ASSEMBLIES INCORPORATING SENSING DEVICES (71) We, RANSOME HOFFMANN POLLARD LIMITED, a British Company of New Street, Chelmsford, Essex CM1 lPU, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to bearing assemblies, incorporating sensing means for sensing positional relationships or motion.

Mechanical assemblies employing electromagnetic tachogenerators are known per se.

However these known assemblies are bulky and complex and there is a need for simpler constructions in which standard units, such as rotary bearings, can be utilized without extensive modification.

UK Patent Specification No. 1504170 relates to a bearing assembly of particularly compact nature where a transducer is built into the assembly alongside the bearing races to sense the movement of one race in relation to the other.

The subject matter of this patent application is divided from our parent UK patent application 30895/77 cognate with 52119/77 serial number (Serial No. 1604861).

According to the present invention a bearing assembly comprises first and second relatively movable parts, means mounted to or associated with the first part for movement therewith and sensing means mounted to or associated with the second part for sensing the movement of said means, wherein said sensing means comprises oscillatory circuit means including an inductive element which is directly energized to produce a magnetic field which is influenced by the passage of said means, and means for producing a signal dependent on said influence and indicative of said movement of the first part.

Thus a bearing assembly constructed in accordance with the invention may comprise first and second relatively rotatable bearing races, rolling elements located between the races, toothed means or its equivalent mounted for rotary movement with the first race to influence a magnetic field and sensing means for sensing the movement of the toothed means, wherein said sensing means comprising an inductive sensor composed of a ferrite rod or the like carrying a coil, oscillatory circuit means for directly energizing the sensor to produce said magnetic field and means for producing a signal dependent on said influence and indicative of the rotary movement of said first race.

In accordance with certain embodiments of the invention the sensing means can be mounted in carrier means or a housing which is arranged at one side of the bearing races and is preferably detachably secured thereto. In other embodiments the housing can be disposed radially inwards or outwards of the bearing races. Thus according to the application or use, the available space can be utilized as appropriate.

A disc with teeth, projections or regions of magnetic or electrically-conductive nature can influence the magnetic field provided by the element or sensor.

The sensing means can provide either a digital or an analogue signal, or both, indicative of speed and/or position.

The invention may be understood more readily, and various other features of the invention may become apparent, from consideration of the following description.

Embodiments of the invention will now be described, by way of examples only, with reference to the accompanying drawings, wherein: Figure 1 is an exploded perspective view of part of the first assembly employing a rolling element bearing and sensing means constructed in accordance with the invention; Figure 2 is an exploded perspective view of part of a second assembly constructed in accordance with the invention; Figure 3 is a circuit diagram depicting one form of sensing means for use in assemblies constructed in accordance with the invention; Figure 4 is a circuit diagram depicting a modified form of sensing means for use in assemblies constructed in accordance with the invention; Figure 5 to 10 are diagrammatic representations of other bearing assemblies constructed in accordance with the invention; Figure 11 is a diagrammatic side view of another rolling element bearing assembly constructed in accordance with the invention; Figure 12 to 15 are sectional side views of further bearing assemblies constructed in accordance with the invention.; Figure 16 is a diagrammatic side view of a portable tachometer instrument constructed in accordance with the invention; Figure 17 is a schematic block diagram of a digital to analogue converter which can be used with the sensing means of assemblies constructed in accordance with the invention; and Figure 18 is a schematic block diagram of a modified form of the sensing means shown in Figure 3 which may be employed in or with the assemblies constructed in accordance with the invention.

Before describing the various assemblies and devices which embody the present invention it is worth emphasizing at this stage in all cases where bearings are used in the assemblies these bearings can be entirely conventional and are unmodified per se or only modified in minor resPeCts.

As shown in Figure 1, a conventional rolling-element bearing 1 has an inner race 10, an outer race 11 and rolling elements, in this case balls 12, therebetween. For convenience, the conventional cage for retraining and spacing the balls 12 is omitted from the drawing and it is assumed for the purposes of illustration that the inner race 10 is rotatable while the outer race 11 is stationary.

In accordance with the invention electronic sensing means is provided for sensing relative movement between the races 10, 11 thereby to provide a signal directly indicative of rotary speed. The sensing means in this embodiment employs a circuit as depicted in Figure 3 and is carried and housed by a component in the form of a carrier ring 13 mounted at the side of the bearing 1. The ring 13 is mounted to the outer race 11 and in this illustrated assembly the ring 1 has a recessed shoulder 13' at its inner side which frictionally engages with corresponding flanks 13" of the outer race 11 as a press fit. As an alternative the ring 13 can be adhesively bonded, or keyed, or clamped, e.g. with screws, to the race 11. A further recess 13A beneath the shoulder 13' of the ring 13 accommodates a futher component in the form of a toothed disc 14 which is designed to co-operate with the sensing means but which does not contact the ring 13. The toothed dise 14 has a flange 15 which is frictionally engaged as a press-on fit with the outer face 15' of the inner race 10. The electrical components of the sensing means, described hereinafter, are collectively designated 16 in Figure 1 and are supported by a printed circuit board 17 conveniently of annular or part annular shape. The printed circuit board 17 is itself mounted in the ring 13, which acts as a housing therefor, in the position denoted by dotted lines 17'. The ring 13 can be a moulded plastics component, preferably made from an epoxy resin. The sensing means includes an inductive sensor or probe 9 in the form of an inductive coil wound onto a ferrite core or rod 18 also mounted to the printed circuit board 17. The ferrite rod 18 adopts the position denoted by dotted lines 18' in the ring 13 and projects parallel to the axis of rotation of the bearing 1 , 11 to terminate closely adjacent the teeth 19 of the disc 14. In general, the movement of the teeth 19 in spaced succession as the disc 14 rotates with the race 10 cause discontinuity sensed by the sensor or probe 9. In this case the disc 14 is an integral metal component with at least the teeth 19 being made from an electrically conductive material in which eddy currents can be produced locally of the rod 18 by an alternating current set up in the inductive coil by an oscillator of the sensing means. The discontinuity produced by the teeth 19 and the gaps therebetween successively moving past the rod 18 give rise to changes in a parameter of the circuit of the sensing means which changes are detected to provide a signal directly indicative of rotary speed.

The operation of the sensing means will be described in more detail in conjunction with Figure As shown in Figure 3 the circuit of the sensing means comprises an R.F. tuned oscillator with a single N-P-N transistor TR1 having its emitter connected via resistors RL1, RL2 to a negative d.c. voltage. A capacitor CL is connected in parallel with the resistor RL2. An output signal is generated across the capacitor CL and is taken off via an output OL. A tuned sub-circuit is composed of a centre-tapped coil T1, T2, wound onto the ferrite core or rod 18 and capacitors Cl, C2 connected in series between the collector and base of the transistor TR1. The coil T1, T2, is connected in parallel with the capacitor C1 and has its centre tap connected to a positive d.c. voltage. A bias resistor R1 is connected between the base of the transistor TR1 and the positive d.c. voltage. The circuit is energized by the positive and negative voltage supplies which may be conveniently combined in a small electric cable C with the output OL. In one practical embodiment of the circuit the following components are utilized.

TR1 BC182 - National (Registered Trade Mark) Semiconductors.

RL1 47Q 1/2 w RL2 820 Q 1/4 w R1 100K11 w T1 12 Turns ) 38 s.w.g. enamelled T2 50 Turns copper wire Ferrite Rod diameter 1.6mm Rod Length 11.5 mm (overall) with or without a modified end portion with a chisel-like shape or a tapered, e.g., frusto-conical shape C1 2200 pF C2 100 pF C3 0.1 ij F CL 0.22 11 F Voltage supply - Typically 12v.

During operation, the circuit oscillates continuously at radio frequency to generate an alternating current directly in the inductive coil T1, T2, and eddy currents are induced in each tooth 19 as the latter moves across the axis of the rod 18. The alternate presence and absence of such eddy currents, corresponding to the alternate presence and absence of a tooth in the vicinity of the rod 18, produces reflected impedance changes in the collector load which produces a variation in the emitter current. This in turn, gives rise to a typical waveform of the type shown in Figure 3 as an output. For a particular spacing between the sensor 9 (18, T1, T2) and the teeth 19 of the disc 14 the waveform has a constant amplitude and if desired the pulsed or square output signal can be amplified and/or additionally processed and shaped to provide a senes of pulses the frequency of which directly represents the rotational speed of the inner race 10. The circuit can be modified as depicted by chain-dotted lines with the components RL2, CL remote, from the sensing means and the output provided on a pair of leads S. The digital signal produced or derived from the sensing device can be utilized in a variety of ways, for example in a comparator fashion, to provide, in other related embodiments, a measure of angular acceleratlon or position for example. In one embodiment, a direct count and visual display of the number of pulses occurring in a specific time period can be produced. In a modified sensing device, described in outline hereinafter in connection with Figure 18, the affect of the teeth 19 on the operation of the oscillator may be detected as a change in phase rather than a change in impedance but nonetheless a digital signal can still be produced which represents rotary speed. Figure 4 depicts a modified circuit where like reference numerals denote like parts to Figure 3. The circuit of Figure 4 has an additional line driver stage 16' fed by the basic oscillator 16. In a practical embodiment of the line driver circuit the following additional components were utilized: L1 22 H SC30/22 R2 1K w R3 1.2 KQl/4w R4 10KQl/4w R5 10K Q 11 w R6 820KQl/4w R7 82011 1/4w R8 1KQ l/4w R9 18 Q w R10 10hl w C4 0.047 y F C5 6.8 11. F C6 0.22 A F Al LM111H National Semiconductors TR2 - BC182 - National Semi conductors TR3 - 2N2222A - National Semi conductors TR4 - 2N2222A-National Semi conductors TR5 - 2N2222A-National Semi conductors In the assembly shown in Figure 2 like reference numerals are used to denote the same features as the assembly described and illustrated in Figures 1 and 3. In contrast to Figure 1 however the assembly of Figure 2 has the orientation of the rod 18 radial to the axis of rotation instead of parallel thereto. The disc 14 can be shaped pressed-on metal, e.g., steel, structure 14A or a more simple plane ring component 14B produced by powder metal technology with projections or teeth 19 around its peripheral. The particular orientation of the sensor 9 in relation to the teeth 19 is not particufarly critical and angular dispositions can be adopted. Also the provision of the disc 14 is not essential and in some bearing assemblies where high accuracy is not needed the objective of providing a speed or position indicative signal can be achieved by simply sensing the movement of the rolhng elements (12) themselves, as is itself described and claimed in the aforementioned UK Patent Specification No. 1504170.

In one specific notable application of the invention the disc 14 and the ring 13 with the sensing means can be mounted to a wholly standard vehicle wheel bearing thereby providing a signal for a digital tachometer. If, for example, a digital display of revs/minute is required the disc 14 can have 60 teeth and a digital counter can count the number of output pulses produced by the sensing means over a one-second period.

In this case the inner race 10 would be stationary on the wheel hub while the outer wheel race 11 would rotate and the positions of the ring 13 and the disc 14 would preferably be reversed. With a front wheel drive vehicle, however, where the inner race 10 rotates and the outer race 11 is stationary the arrangement as illustrated can be adopted without alteration.

The sensing means as described may also be incorporated or used with a variety of other forms of bearings. Figures 5 to 10 depict examples of other forms of bearings where again like reference numerals denote the same or analogous components to Figures 1 to 4. Thus Figure 5 has a rotating inner race 10 and balls 12 as rolling elements but the outer race 11 is here in angular contact with the balls 12. Figure 6 represents a thrust bearing with load plates 20, 21. Figure 7 represents a roller bearing, Figure 8 a tapered roller bearing, Figure 9 a spherical bearing and Figure 10 a lain bearing. In all cases provision of the separate disc 14 and the rin 13 and the sensing device does not affect the design and operation of the bearings which can be quite standard.

The sensing means need not detect rotary movement only and linear movement can be detected by utilizing a moving rack or the like in place of the disc 14.

In some applications the movement which is to be detected is especially rapid and a disc or rack with a large number of teeth, such as is illustrated, would cause the circuit to reach the limits of its response time in relation to the transisitions producing the square wave. In these cases it is easy to use a component with just one tooth or a few teeth. For example, with a high speed rotary bearing a single tooth on the periphery of the disc 14 would produce one pulse per revolution. The use of toothed components and metal components is also not essential to the operation of the sensing means as described. It is only necessary to produce some discontinuity in the path of relative movement of a conductive or magnetic influence sufficient to affect the operation of the oscillator of the sensing means to provide the necessary detecting function. In one simple alternative arrangement, especially applicable to rotary bearings, a plastics ring may carry a series of discrete discs, or slugs, or other bodies, of metal, such as brass or aluminium, seated into holes or bonded to the ring and these metal bodies would act in analogous fashion to the individual teeth described hereinbefore. In the case of high speed bearings again a single metal body on the plastics device may suffice. Instead of metal bodies one or more discrete magnets can be carried by the plastics ring and here there would be flux linkage between the individual magnet or magnets and the inductive coil T1, T2, of the sensing device. Otherwise the operation and construction of the sensing device and the assemblies utilizing the same can be as described above.

Although the use of the printed circuit board and the carrier ring 13 for the sensing device is quite practicable and has certain advantages with small scale production other methods of construction for the sensing device can be adopted. Thus in one method the individual electrical components of the sensing device are wired in a jig mould and the mould filled with plastics, such as epoxy resin, preferably by injection moulding to encapsulate the electncal components and form a permanent housing (c.f. the ring 13) therefor. In another method of construction a flexible printed circuit carrying the electrical components is disposed around a desired bearing circumference and then a plastics material is again used to encapsulate all the components. One advantage of this technique would be that a standardized printed circuit board can be used to provide a variety of sizes of housings to match a range of bearings.

The circuit of Figure 3 or 4 is eminently susceptible to an integrated circuit conveniently encapsulated or merely embedded in a structure such as the carrier ring 13. The circuit can also be constructed by thick or thin film techniques where the circuit components are deposited on substrates such as glass or ceramic forming part or all of a structure such as the carrier ring 13. Again a standard circuit can be used for a variety of different sized carrier or housing components. Even with standard electrical components the device can be compact and additional electronic circuits and devices can easily be incorporated into the bearing assembly.

Figure 11 depicts another rotary bearing employing a sensing device here mounted in another fashion. The bearing as depicted has a conventional cage 28 locating the ball 2 between the inner race 10 and the outer race 11. A conventional flexible seal 30 is locate at one side of the bearing between the races 10, 11 and is fitted to the outer race 11. A flexible cover 32 complementary to the seal 30 and incorporating an integrated circuit chip 31, for example, or some other means embodying the sensing means or circuit of Figure 3 or 4 except for the coil, is located at the other side of the bearing. The cover 32 can also be fixed to the outer race if desired but in any event remains stationary and also performs a sealing function. A toothed ring or analogous component 34 is again mounted to the inner race 10.

The ferrite core or rod 18 carrying the electrical coil extends radially to intersect the path of movement of the discontinuity of the component 34 and the rod 18 is mounted to the cover 32.

In the embodiment illustrated in Figure 12 a bearing assembly has a sleeve 49 with a pair of O-rings 45 on its inner surface. The sleeve 49 has a flange 50 at one end which locates a toothed disc 14. A sensor unit or housing 42 is arranged concentrically with the sleeve 49. A standard rolling element bearing 1 represented schematically and having inner and outer rings or races (e.g., as in Figure 1) is disposed between the sleeve 49 and the housing 42 to render these components relatively rotatable. A spacer 44 locates between the bearing 1 and the disc 14. The housing 42 contains sensing means which may be constructed as described and illustrated in Figure 3 or 4. The components of the sensing means are again mounted on a printed circuit board 17 and the ferrite rod or probe 18 projects across the external periphery of the toothed disc 14. A dust shield 43 is snap-fitted between the flange 50 of the sleeve 49 and a recessed shoulder in the housing 42. The assembly as described can be mounted onto a shaft or spindle 41 which projects into or through the sleeve 49. The housing 42 can be held stationary by any suitable means and rotation of the spindle 41 moves the teeth of the disc 14 passed the probe 18. The sensing means then operates to produce a rotary speed-indicative signal as described.

In the embodiment depicted in Figure 13, like reference numerals are used to denote like parts to Figure 12. In the Figure 13 embodiment, an adaptor 29 is used to rotatably connect the sleeve 49 to a rotary part (not shown) of generally smaller diameter than the shaft of spindle 41 of Figure 1 and the O-rings 45 are omitted. A rod 36 is used to engage with a bracket or the like (not shown) thereby to lock the housing 42 in a stationary position. A detachable cover 38 is provided to provide access to the housing 42.

In the embodiment depicted in Figure 14 again like reference numerals are used to denote like parts to Figures 12 and 13. In contrast to the assemblies of Figures 12 and 13, however, the stationary housing 42 of Figure 14 is provided at the inside of the assembly and is held by a sleeve 51. The toothed disc 14 here has the teeth on its inner periphery for movement passed the probe 18 of the sensing means. The toothed disc 14 is mounted to a flanged cylindrical member 52 which rotates relative to the housing 42 and the sleeve 51 which are preferably held stationary. As illustrated, a cylindrical part 53, which may be the hollow end portion of a shaft or the like, is engaged with the member 52 so that the sensing means provides a signal indicative of the rotation of the part 53.

Figure 15 depicts a modified assembly similar to Figures 11 and 12 and particularly designed for use with speedometer cables of motor vehicles. In Figure 15, like reference numerals again denote like parts to the previously-described embodiments. A structural member 60 normally part of a gearbox, contains a rotatable coupling 61. The member 60 has an external threaded region 60' which normally receives an internally-screw threaded region 62' of a conventional speedometer cable end cap 62. The inner square-sectioned rotatable core 63 of the speedometer cable would normality locate directly with the coupling 61. In the illustrated assembly, however, the core 63 is extended to project through the basic bearing 1 and engages in a square piercing 64 in the sleeve 49. The housing 42, containing the sensing means, engages with two cylindrical bodies 65, 66. The body 65 is threaded internally to mate with the threaded region 60' of the member 60 while the body 66 is threaded externally to receive the threaded region 62' of the cap 62. Thus the bodies 65, 66 hold the housing 42 stationary. The rotary movement of the coupling 61 drives the core 63 to operate the speedometer in the usual manner. In addition, the core 63 rotates the sleeve 49 and the toothed disc 14 and the sensing means produces a signal indicative of this rotary speed.

It is desirable to provide the body 65 with a cooling fin 68 and to manufacture this body 65 and preferably also the body 66 from a material such as an aluminium or duralumin to act as a heat shield for the housing 42 and the electronic components therein.

In the assemblies as described and illustrated in Figures 12 to 15 the electrical cables or leads denoted by dotted lines 40 and connecting to the sensing means can be taken out at any convenient region and not necessarily in the position as illustrated.

Figure 16 depicts a portable tachometer instrument which employs an assembly of the type shown in Figures 12 and 13. This assembly is mounted at one end of a housing 90, sonveniently made of synthetic plastics. A cap 91 at this end of the housing 90 has a central tore 96 and a connector 92 here in the form of a conical member projects through the bore 96. The connector 92 is conveniently detachably fitted, e.g., by a push-fit into the sleeve 49 which is rotatably secured to the inner race of the bearing. The connector 92, which can be replaced to suit a particular application, can be mated to any rotatable mechanism or device and then the rotation of the toothed wheel or disc 14 produces the speed indicative signal as before. The speed-indicative signal is processed by means in the interior 97 of the housing 90 and displayed as a digital readout 93 visible from the side of the housing 90. The power for the sensing means 16 can be provided by re-chargeable batteries (not shown) mounted in a space 94 of the housing 90. A socket 95 at the opposite end of the housing 90 serves to connect the batteries to a charging unit or supply.

As mentioned previously additional electronic circuits and devices can be provided to process the waveform produced by the basic circuit of Figure 3.

Figure 17 depicts an example of an additional processing circuit in the form of a digital to analogue converter for the sensing means of Figure 3 or 4. In Figure 17, the oscillator and detector circuit of Figure 3 or 4 is designated 70 and the output therefrom is optionally fed through an amplifier and shaper 71 to drive a monostable circuit 72. The sharp square wave digit output produced by the circuit 72 has a frequency representing motion and the output of the circuit 72 is fed to an integrator 73 which provides an analogue voltage the amplitude of which is proportional to motion. The analogue output from the integrator 73 is finally amplified by an amplifier 74.

Figure 18 represents an alternative form of detecting operation for producing a waveform from the sensing means related to the rotary motion or position in which the change in phase in the alternating current in the oscillator is sensed. In Figure 18 the oscillator of Figure 3 or 4 denoted 70 feeds a phase shift detector 80 which produces a pulsed waveform related to speed and this waveform is amplified by amplifier 81 and shaped by shaper 82 to provide a more regular square waveform.

WHAT WE CLAIM I:- 1. A bearing assembly comprising first and second relatively movable parts, means mounted to or associated with the first part for movement therewith and sensing means mounted to or associated with the second part for sensing the movement of said means, wherein said sensing means comprises oscillatory circuit means including an inductive element which is directly energized to produce a magnetic field which is influenced by the passage of said means, and means for producing a signal dependent on said influence and indicative of said movement of the first part.

2. A bearing assembly comprising first and second relatively rotatable bearing races, rolling elements located between the races, toothed means or its equivalent mounted for rotary movement with the first race to influence a magnetic field and sensing means for sensing the movement of the toothed means, wherein said sensing means comprising an inductive sensor composed of a ferrite rod or the like carrying a coil, oscillatory circuit means for directly energizing the sensor to produce said magnetic field and means for producing a signal dependant on said influence and indicative of the rotary movement of said first race.

3. An assembly according to claim 2, wherein the ferrite rod extends closely adjacent the teeth of the toothed means and is disposed with its longitudinal axis parallel to the axis of relative rotation of the bearing races.

4. An assembly according to claim 2 or 3, wherein the sensing means is supported by carrier means connected directly to the second race.

5. An assembly according to claim 2, 3 or 4, wherein the sensing means is disposed wholly within a boundary defined by an axial projection of the radially-outermost surface of the bearing races.

6. An assembly according to claim 4, wherein the carrier means is fixed to a side face of the second bearing race and the sensing means, carrier means and the toothed means are collectively disposed within a boundary defined by an axial projection of the radially outermost surface of the bearing races.

7. An assembly according to claim 5 or 6, wherein the sensing means or the col

Claims

**WARNING** start of CLMS field may overlap end of DESC **. In the assemblies as described and illustrated in Figures 12 to 15 the electrical cables or leads denoted by dotted lines 40 and connecting to the sensing means can be taken out at any convenient region and not necessarily in the position as illustrated. Figure 16 depicts a portable tachometer instrument which employs an assembly of the type shown in Figures 12 and 13. This assembly is mounted at one end of a housing 90, sonveniently made of synthetic plastics. A cap 91 at this end of the housing 90 has a central tore 96 and a connector 92 here in the form of a conical member projects through the bore 96. The connector 92 is conveniently detachably fitted, e.g., by a push-fit into the sleeve 49 which is rotatably secured to the inner race of the bearing. The connector 92, which can be replaced to suit a particular application, can be mated to any rotatable mechanism or device and then the rotation of the toothed wheel or disc 14 produces the speed indicative signal as before. The speed-indicative signal is processed by means in the interior 97 of the housing 90 and displayed as a digital readout 93 visible from the side of the housing 90. The power for the sensing means 16 can be provided by re-chargeable batteries (not shown) mounted in a space 94 of the housing 90. A socket 95 at the opposite end of the housing 90 serves to connect the batteries to a charging unit or supply. As mentioned previously additional electronic circuits and devices can be provided to process the waveform produced by the basic circuit of Figure 3. Figure 17 depicts an example of an additional processing circuit in the form of a digital to analogue converter for the sensing means of Figure 3 or 4. In Figure 17, the oscillator and detector circuit of Figure 3 or 4 is designated 70 and the output therefrom is optionally fed through an amplifier and shaper 71 to drive a monostable circuit 72. The sharp square wave digit output produced by the circuit 72 has a frequency representing motion and the output of the circuit 72 is fed to an integrator 73 which provides an analogue voltage the amplitude of which is proportional to motion. The analogue output from the integrator 73 is finally amplified by an amplifier 74. Figure 18 represents an alternative form of detecting operation for producing a waveform from the sensing means related to the rotary motion or position in which the change in phase in the alternating current in the oscillator is sensed. In Figure 18 the oscillator of Figure 3 or 4 denoted 70 feeds a phase shift detector 80 which produces a pulsed waveform related to speed and this waveform is amplified by amplifier 81 and shaped by shaper 82 to provide a more regular square waveform. WHAT WE CLAIM I:-

1. A bearing assembly comprising first and second relatively movable parts, means mounted to or associated with the first part for movement therewith and sensing means mounted to or associated with the second part for sensing the movement of said means, wherein said sensing means comprises oscillatory circuit means including an inductive element which is directly energized to produce a magnetic field which is influenced by the passage of said means, and means for producing a signal dependent on said influence and indicative of said movement of the first part.

7. An assembly according to claim 5 or 6, wherein the sensing means or the collective combination of the sensing means, carrier means and the toothed means is, or are, disposed wholly within the axially and radially outermost surfaces of the bearing races.

8. An assembly according to claim 2, 3 or 4, wherein the sensing means is disposed predominantly within boundaries defined by radial projections of the axial outer side faces

of the bearing races.

9. An assembly according to claim 4, wherein the carrier means is located to a peripheral surface of the second bearing race and wherein the sensing means, the carrier means and the toothed means are collectively disposed predominantly within boundaries defined by radial projections of the axial outermost surfaces of the bearing races.

10. An assembly according to claim 4, 6 or 9, wherein the carrier means is annular and is disposed symmetrically relative to the axis of rotation between the bearing races.

11. An assembly according to any one of claims 2 to 10 and further comprising display means for displaying a read-out indicative of the rotary speed of the first race and coupling means for selectlvely coupling the first race to an object, the rotary speed of which is to be displayed.

12. An assembly according to claim 4, or according to any one of the preceding claims when appended to claim 4, wherein the sensing means is supported within the carrier means.

13. An assembly according to claim 3, or according to any one of the preceding claims when appended to claim 3, wherein the ferrite rod extends beyond projections of the axial side faces of the teeth of the toothed means.

14. An assembly according to claim 2, wherein the ferrite rod is disposed in a position with its axis normal to the axis of relative rotation between the races and wherein the axial extent of the teeth of the toothed means is larger than the width or diameter of the ferrite rod such that a projection of the outer surface of the ferrite rod is located within the axial extent of said teeth.

15. An assembly according to any one of the claims 2 to 14, wherein the oscillatory circuit means is adapted to oscillate continuously at radio frequency and comprises a single transistor with a tuned load circuit and wherem the inductive sensor comprises a single centre-tapped coil on the ferrite rod in the tuned load circuit whereby the signal-producing means develops a voltage which varies in proportion to the current flowing through said transistor.

16. An assembly according to any one of claims 1 to 14, wherein the oscillatory circuit means is adapted to directly and continuously energize the inductive element or sensor.

17. An assembly according to claim 9, or according to any one of claims 10, 11, 12, 13, 15 or 16 when appended to claim 9, wherein the peripheral surface is radially external to the bearing races.

18. An assembly according to claim 9, or according to any one of claims 10, 11, 12, 13, 15 or 16 when appended to claim 9, wherein the peripheral surface is radially internal to the bearing races.

19. An assembly according to any one of claims 1 to 18, wherein the signal-producing means produces a digital signal.

20. An assembly according to any one of claims 1 to 18, wherein the signal-producing means produces an analogue signal.

21. An assembly according to any one of the preceding claims, wherein the signal produced by the signal-producing means is dependent on a change in the frequency or phase of an oscillatory signal generated by or derived from the oscillatory current means.

22. An assembly according to claim 1, wherein the means mounted to or associated with the first part is formed with electrically conductive or magnetic elements the passage of which are sensed.

23. An assembly according to claim 1, wherein the means mounted to the first part is a disc provided with spaced discrete projections or teeth or bodies constituting elements the passage of which is sensed.

24. An assembly according to any one of claims 2 to 21, wherein the toothed means or its equivalent takes the form of a disc provided with spaced, discrete projections or teeth or bodies constituting elements the passage of which is sensed.

25. An assembly substantially as described with reference to, and as illustrated in, any one or more of the Figures of the accompanying drawings.