EP0457796A1

EP0457796A1 - Positive displacement wing motor

Info

Publication number: EP0457796A1
Application number: EP19900902649
Authority: EP
Inventors: John Richard Neville Roe; Hector Fillipus Alexander Van Drentham-Susman; John Edward Doubenmier
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-02-09
Filing date: 1990-02-07
Publication date: 1991-11-27
Also published as: AU5031490A; WO1990009510A1

Abstract

Le moteur décrit, qui est conçu pour être utilisé dans des opérations de forage est constitué par un moteur à ailettes et comprend un carter généralement tubulaire (1, 2) et un rotor (4) monté en rotation dans le carter et espacé radialement de lui, de façon à définir une chambre (18) entre eux. Le carter (1, 2) est pourvu d'organes d'entrée et de sortie angulairement espacés (19, 20), permettant l'admission du fluide de travail pressurisé depuis un conduit d'entrée (19a) se trouvant dans le carter (1, 2) jusqu'à dans la chambre et l'émission de ce fluide depuis l'intérieur de la chambre, vers un conduit de sortie (20a) séparé du conduit d'entrée (18) par une paroi (21). Le carter (2) comporte une paroi s'étendant généralement radialement (3), qui s'étend essentiellement en contact avec le rotor (4) en une position angulaire située entre les organes de sortie et d'entrée (20, 19). Le rotor (4) comprend plusieurs ailettes angulairement espacées (15). La paroi s'étendant radialement (3) ou l'ailette (15) est déplaçable depuis une disposition saillante s'étendant généralement radialement en contact essentiellement étanche avec le rotor (4) ou le carter (1, 2), respectivement, vers une disposition généralement repliée, lorsque l'organe en question traverse l'autre organe, à savoir la paroi s'étendant radialement (3) ou l'ailette (15). Les ailettes (15) et les organes d'entrée et de sortie (19, 20) sont formés, conçus et disposés angulairement entre eux, de sorte qu'un courant de fluide pressurisé dans la chambre (18) agit contre un côté amont (15c) d'une première ailette (15') de façon à faire tourner le rotor, tout en permettant l'évacuation du fluide depuis son côté aval (15e), jusqu'à ce que l'ailette (15') traverse l'organe de sortie (20) et qu'une seconde ailette (15'') traverse l'organe d'entrée (19), le processus pouvant alors se répéter. La présente invention se rapporte également à des appareils de forage et de carottage équipés d'un moteur à ailettes de la présente invention.The motor described, which is designed to be used in drilling operations, consists of a fin motor and comprises a generally tubular casing (1, 2) and a rotor (4) rotatably mounted in the casing and spaced radially from it. , so as to define a chamber (18) between them. The housing (1, 2) is provided with angularly spaced inlet and outlet members (19, 20), allowing the admission of the pressurized working fluid from an inlet duct (19a) located in the housing ( 1, 2) to the chamber and the emission of this fluid from inside the chamber, to an outlet duct (20a) separated from the inlet duct (18) by a wall (21). The housing (2) has a generally radially extending wall (3), which extends essentially in contact with the rotor (4) in an angular position located between the output and input members (20, 19). The rotor (4) comprises several angularly spaced fins (15). The radially extending wall (3) or the fin (15) is movable from a projecting arrangement generally extending radially in essentially sealed contact with the rotor (4) or the housing (1, 2), respectively, towards a generally folded arrangement, when the member in question crosses the other member, namely the radially extending wall (3) or the fin (15). The fins (15) and the inlet and outlet members (19, 20) are formed, designed and arranged angularly therebetween, so that a stream of pressurized fluid in the chamber (18) acts against an upstream side ( 15c) of a first fin (15 ') so as to rotate the rotor, while allowing the discharge of the fluid from its downstream side (15e), until the fin (15') crosses the outlet member (20) and a second fin (15 '') passes through the inlet member (19), the process then being able to be repeated. The present invention also relates to drilling and coring apparatuses fitted with a fin motor of the present invention.

Description

"POSITIVE DISPLACEMENT WING MOTOR" The invention relates to a hydraulically or pneumatically driven wing motor especially but not exclusively for use as a drilling tool in the oil, mining or civil engineering industry for directional including horizontal as well as straight hole drilling or as a top drive to drive a "Drill String". Down hole motors as generally used in the oil and mining industries suffer from the disadvantages^"that they are very long, heavy and expensive to manufacture.

A motor suitable for use in down-hole drilling applications, characterised in that said motor is a wing motor and comprises a generally tubular casing and a rotor mounted for rotation within said casing and substantially radially spaced therefrom so as to define a chamber therebetween, said casing being provided with angularly spaced apart inlet means and outlet means for ingress of pressurised working fluid from inlet conduit means in. said casing into said chamber and egress of said fluid from within said chamber, to outlet conduit means separated from said inlet conduit means by wall means, in use of the motor, said casing having generally radially extending wall means extending substantially into contact with said rotor at an angular position between said outlet means and said inlet means, said rotor having a plurality of angularly spaced apart wing means, one of said radially extending walls means and said wing means being displacable from a generally radially projecting configuration in substantially sealing engagement with said rotor or said casing respectively, to a generally retracted configuration when traversing the other of said radially extending wall means and said wing means, said wing means and inlet and outlet means being formed and arranged and relatively angularly disposed so that/ in use of said motor, a flow of pressurised fluid into said chamber acts against an upstream side of a first said wing means so as to rotate said rotor while venting fluid from its downstream side until said wing means traverses said outlet means and a second said wing means traverses the inlet means whereupon said process is repeated.

Advantageously, the casing is in the form of inner and outer casings with the inlet and outlet conduit means defined therebetween. Preferably the inlet and outlet conduit means are longitudinally spaced at opposite sides of an annular wall.

Thus in one, preferred, form of the invention the wing means of the rotor are formed and arranged so as to be displacable from a generally radially projecting configuration in substantially sealing engagement with the casing, to a generally retracted configuration when traversing the radially extending wall means; and in another form of the invention, the generally radially extending wall means of the casing are formed and arranged so as to be displacable from a generally radially projecting configuration in substantially sealing engagement with the rotor, to a generally retracted configuration when traversing the wing means.

In use of the motor, pressurised working fluid acts against the upstream side of the wing means thereby to rotate the rotor while venting at the downstream side.

The motor of the present invention may thus be of quite short, light and inexpensive construction and can be produced using more or less conventional manufacturing techniques.

Advantageously, said rotor and casing are provided with, directly or indirectly, inter-engagable drive transmission means formed and arranged to allow the rotor to be driven by the casing in the case of wing failure. In this case the motor casing may be, for example, rotated by the drill pipe or "string".

Conveniently, the non-retractable form of the generally radially extending wall means or wing means, comprises longitudinally extending cams along the interior wall surface of the casing or the outer wall surface of the rotor so as to provide progressive displacement of the wing means or radially extending wall means from their projecting positions to their retracted positions. Advantageously, the inlet and outlet means comprise a plurality of discretely formed inlet and outlet ports in the inner casing. The rotor or casing, as appropriate, is provided with a plurality of slot means formed and arranged for containing respective ones of the wing means or radially extending wall means, in their retracted position in preferred embodiments.

The retractable wings (or radial walls) may be formed and arranged so as to be angularly retractable from a generally radially extending configuration to a generally circu ferentially extending configuration. Preferably though they are formed and arranged so as to be generally radially retractable.

Conveniently, the angularly retractable wing means or radially extending wall means are made from vulcanised neoprene or other suitable resiliently deformable polymeric material, desirably with metal reinforcement.

Advantageously, the rotor has an odd number of wings^■ in order to avoid 'dead spots and possible 'stalling' of the rotor in a symmetrically disposed position relative to the inlet and outlet ports.

Further preferred features and advantages of the invention will appear from the following detailed description given by way of example of some preferred embodiments illustrated with reference to the accompanying drawings wherein:

Fig. 1 is a sectional side view of a first embodiment ό^~f a wing motor in accordance with the present invention;

Fig. 2 is a sectional view of the wing motor of Fig. 1 taken along line I - I with modified inlet and outlet ports; Fig. 3 is a sectional view of a typical bearing assembly and thrust block of the wing motor of Figs. l and 2;

Fig. 4 is a sectional view corresponding to that of Fig. 2 of a modified embodiment (outer casing not shown) .

Fig. 5 is a sectional view corresponding to Fig. 2 of a further embodiment;

Fig. 6 is a detail sectional view corresponding to Fig. 5 showing a first hydraulically operated wing;

Fig. 7 is a detail sectional perspective view showing a wing similar to that of Fig. 6; and Fig. 8 is a detail sectional view generally similar to

Fig. 6 of a modified form of hydraulically operated wing.

Referring to Figs. 1 and 2 of the drawings, a first embodiment of a wing motor in accordance with the present invention comprises a tubular outer casing 1, a concentric inner casing running-liner 2 with generally radially inwardly projecting wall means in the form of longitudinally extending wing deflector cams 3 (see Fig. 2) which form a stator for the wing motor, and a rotor 4 running in low friction plastics material bearings 5 at either end 4a, b. Suitable plastics include PTFE (e.g. Teflon and polyamide-polyimide (e.g. TorIon) .

A drive end 6 of the motor 4 is connected by a splined coupling sleeve 7 to a stub shaft 8 on which a split ring 9 is mounted to contain the bearing races and transfer axial forces from the shaft 8 to a bearing assembly housing 10. The stub shaft 8 is mounted in the bearing housing 10 which also acts as the thrust block for the wing motor and forms an extension of a drive member 11 containing a drill bit or other tool engagement socket 12. The rotor 4 is rotatably supported in the outer casing 1 via the low friction bearings^" 5 which are mounted in bearing housings 14 which are in turn disposed in -5-

casings ends 14a. which are screw threadedly engaged 14b with the outer casing 1 of the motor.

The rotor is provided with two pairs of diametrically opposed and circumferentially spaced slots 16, along one, leading, longitudinal edge 16a_ of which is secured an edge 15a of an elongate longitudinally extending wing 15 which projects generally radially outwardly from the rotor 4 to contact the inner casing 2 with its distal edge 15b. Each wing 15 is fashioned from a vulcanised neoprene or other resiliently deformable polymeric material reinforced by a metal insert strip 17 at its trailing side 15c. A generally annular space 18 is defined between the rotor 4 and inner casing 2 and is divided by the two diametrically opposed wing deflector cams 3 into first and second chambers 18a, 18b. Each of said chambers 18a., 18b is provided at a longitudinally upstream end 18c. with inlet means in the form of several inlet ports 19 and at a longitudinally downstream end 18d, with outlet means in the form of several outlet ports 20 for the passage of pressurised working fluid there¬ through as indicated by the arrows thereat.

The illustrated motor is mainly utilised in down-hole applications and is particularly useful for directional drilling. Pressurised drilling fluid or mud is used to rotate the motor rotor 4 and thereby to drive the drill member 11. The fluid enters the chambers 18a, b through the inlet ports 19 and exits through outlet ports 20. As may be seen in Fig. 2, two first wings 15 2, projecting across respective ones of the chambers 18a, b are exposed to high pressure working fluid entering through the inlet ports 19 at their trailing sides 15c thereby exerting a clockwise (as viewed in Fig. 2) turning moment on the rotor 4. The other pair of wings 15 is pressed down into their retra ed positions in the slots 16 by the wing deflector cams 3. When the rotor 4 has turned approximately 20° further in the clock-wise direction under the influence of the fluid pressure

1 on the first mentioned wings 15 in the chambers 18a, b

^•___. the retracted wings 15 will clear the wing deflector cams 3 and be resiliently restored into their projecting positions with their trailing sides 15c exposed to the hydraulic pressure of the working fluid entering through the inlet ports 19 and so in turn exerting a turning moment on the rotor 4 thereby ensuring a continuous rotating and driving force on the rotor 4 with a torque substantially directly proportional to the pressure of the working fluid.

The exhausted working fluid at the leading faces 15e of the wings 15 is compressed between the advancing leading faces 15e and the respective opposed wing deflector cams 3 and displaced longitudinally along the chamber to be expelled out of the outlet ports 20 at the longitudinally downstream end of the inner casing 2, into an annular outlet conduit means 20a_. defined between the inner and outer casings 2, 1 and separated from inlet conduit means 19a_., between the inner and outer casings 2, 1 at their upstream ends adjacent the inlet ports 19, by an annular bearing seal 21. Conveniently the wing deflector cam means 3 could be inclined slightly so as to wind helically clockwise as viewed in Fig. 1 towards the lower outlet end of the motor so as to facilitate progressive longitudinal displacement of exhausted working fluid towards the outlet ports as the rotor wings 15 advance. Alternatively the wings 15 could be formed with a slight helical twist so as to provide a similar effect.

The bearing housings 14 have a notched or castellated circumferential portion 22 connecting the inlet and outlet conduits 19a, 20a with main inlet 23 and outlet 24 of the motor, respectively. From main outlet 24, the exhausted working fluid flows through channels 25 in the splined coupling 7 to a further channel 26 and thence to the drill bit mount 12 where it finally leaves the drill string and may be used as coolant and lubrication means for the drill bit or other tool driven by the motor. The splined coupling 7 contains a seal 27 preventing exhausted working fluid from entering a bearing lubricant space 28 and so contaminating the lubricant contained by this space to lubricate tool holder 12 bearings 29. A further seal 30 prevents lubricant loss by seepage from the bearing lubricant space 28.

In case of possible malfunctions of the motor, pawl means 31 may be included in line with the wings 15 for engagement • with steep end faces 3a of the wing deflector cams 3 adjacent the inlet ports 19 so that when the motor casing 1, 2 is driven in a clockwise direction the pawl means 31 will lock against the wing deflector cam end faces 3a thereby transmitting torque to the rotor 4 and thereby to the drive shaft 11 and tool mount 12 to rotate the drill bit or other tool. The motor is thus in effect self locking.

It will be appreciated that various modifications may be made to the abovedescribed embodiment without departing from the scope of the present invention. Thus, for example, in place of the annular separation seal 21 between the inlet and outlet conduit means there could be provided generally longitudinally extending walls means, the bearing housing circumferential portions being apertured so as to restrict communication between the main inlet and outlet 23, 24 to respective ones of the inlet and outlet conduits 18a_, b_.

It may also be noted that whilst Fig. 1 shows generally radially extending inlet and outlet ports 19, 20, Fig. 2 shows modified, near-tangentially, extending ports for improving the flow of the working fluid therethrough during rotation of the rotor 4. It may further be noted that the inlet and outlet ports are relatively large and that they are longitudinally spaced and separated by a generally annular wall means providing a relatively large cross-sectional area annular flow passage for the fluid between the inner and outer casings, and a large cross-sectional area flow passage through the ports. With such an arrangement it is possible to operate the motor with relatively high fluid pressure but low fluid flow speeds, corresponding to high torque and low speed rotor operation, the speed being generally below 1000 r.p.m. for example, from 100 to 200 r.p.m. for a 200 mm diameter motor and from 600 to 1000 r.p.m. for a 50 mm diameter motor, and at generally corresponding speeds for other sizes. This is particularly advantageous where relatively abrasive fluids such as drilling mud are used to drive the motor since wearing of the motor parts which is a major problem at high flow rates is substantially avoided at low speeds.

It will also be appreciated that the drilling mud flow required for cooling of the drill bit etc. will usually be in excess of that passing through the wing motor. Accordingly there is desirably provided a central axial bore 32 which allows part of the fluid flow from the main inlet 23 to by-pass- the -rotor chambers 18a., b_ and pass directly to the drill-bit holder 12 via a suitable throttle or nozzle means 33. As an alternative the latter could be disposed at the upper end 34 of the rotor 4 in the bearing housing 14 thereat whereby there could be used a drop nozzle which could be more or less readily changed with the aid of, for example, a wire line overshot fishing tool, to allow variation of the distribution of the drilling mud flow between the rotor chambers 18a., b and the by-pass passage 32, e.g. for rotor speed control.

Another modification that may advantageously be made to the abovedescribed embodiment is the use of a larger number of wings relative to the number of angularly differently disposed inlet and outlet ports, in order to reduce wear on the wings arising from subjecting of the wing 15 coming into engagement with the deflector cam 3 to the full fluid pressure entering the chamber 18a_., b_ behind it, by ensuring that at least one wing 15 is always disposed between the inlet ports 19 and the wing 15 coming into engagement with the cam 3.

It will also be understood that the P.T.F.E. bearings 5 in which the rotor ends 4a_, b_ are rotatably supported, also act as seals preventing leakage of fluid from the main inlet 23 directly into the chambers 18a, b bypassing the inlet ports 19 etc. thereby resulting in loss of drive efficiency. In the case of smaller size motors particularly, there could advantageously be provided additional conventional sealing means such as '0' rings 34 on the annular end face 35 of the main body of the rotor 4 to improve sealing in view of the practical limits on manufacturing tolerances as they affect the interfacing of the rotor and the P.T.F.E. bearing 5.

The embodiment of Fig. 4 is generally similar to that of Figs 1 to 3, like parts corresponding to those of the latter embodiment being indicated by like reference num- bers. In the motor of Fig. 4 however the generally radially inwardly projecting wall means of the inner casing running-liner 2, are in the form of elongate long¬ itudinally extending resiliently deformable polymeric e.g. rubber, blades 36 which are receivable in parallel adjacent circumferentially spaced slots 37 in generally similar manner to the from and arrangement of the flexible wings 15 of the first embodiments. Similarly the wings of the rotor 4 are in the form of generally rigid longitudinally extending radially outwardly projecting deflector cams 38 which deflect the blades 36 into their slots 37 as they tra¬ verse the cams 38. In order to avoid dead spots in the rotational movement of the rotor 4, the latter is provided with three or another odd number of wings 38.

Various modifications may be made to the abovedescribed embodiments without departing from the scope of the present invention. Thus for example the flexible rubber blade wall means 36 or wing means 15 could be replaced with generally rigid elements hingedly interconnected for folding about a hingeing axis generally within the slot 37 or 16, respect- ively.

Fig. 5 is a view corresponding to that of Fig. 2 of yet another embodiment showing an alternative form of retractable wing means 39. More particularly the wing means of this embodiment are in the form of generally rigid strips 40 of a polymeric or metallic material located in radially inwardly extending slots 41-which extend generally longitudinally along the outer face 42 of the rotor 4. The radially inner edges 43 of the strips 40 are engaged by resilient biasing means conveniently in the form of helical springs 44 which seat against the base 45 of the respective slot 41 so as to urge the strip 40 outwardly into sealing engagement with the liner 2. As the strips 40 traverse the wing deflector cams 3 they are urged inwardly of the slots 41 to their retracted positions therein.

In order to maximise sealing of the strips 40 against the liner 2 the slots 41 are provided at their trailing sides 46 with fluid passage means in the form of grooves 47 leading from the outer face 42 of the rotor 4 to the base 45 of each slot 41 thereby exposing the radially inner edge 48 of each strip 40 to substantially full pressure working fluid. Insofar as the outer edge 49 of the strip 40 will mostly be in sealing engagement with the liner 2 this will not be exposed to the same pressure whereby the strip 40 will be subjected to a differential pressure tending to urge it outwardly into sealing engagement with the liner. It will be appreciated that as the rotor speed increases in use of the motor the strips 40 are subjected to centrifugal forces which also tend to increase sealing against the liner 2. These forces are however relatively small due to the generally low speeds at which the motor is normally operated.

Fig. 6 shows a modified form of rotor 4 in which the base 45 of the slot 41 in which the wing 49 is mounted, is connected to central axial bore bypass passage 32 by a plurality of radial bores 50 in which are slidably mounted small piston elements 51. By virtue of the pressure differential which normally exists between the drilling mud or other hydraulic fluid in the central bypass passage 32 and that in the rotor chambers 18a,18b (between the rotor 4 and the inner casing 2) - typically the former could be lOOOpsi and the latter 900psi - the piston elements 51 are urged radially outwardly towards the inner casing 2 into sealing engagement with the inner casing 2. As the rotor 4 turns and begins to engage the radially inwardly extending wall means 3, the latter tends to drive the wing 49 together with the piston element 51 radially inwardly to their retracted positions. In order to minimize the resistance to this retraction arising from so-called differential sticking between the wing 49 and inner casing 2, the radially outer end face 52 of the wing 49 is recessed 53 at the trailing edge side 54. Also to facilitate retraction of the wing 49, small grooves 55 are provided in the trailing face 56 of the wing 49 for the passage of fluid displaced from the slot 41 by the returning wing 49. Advantages of such hydraulically operated wing means include the significantly greater force that can be exerted on the wing as compared with mechanical means such as springs and greater reliability. Fig.7 shows part of a rotor 4 generally similar to that of Fig.6 with the wing 49 in its radially outwardly projecting configuration with the grooves 55 clearly visible on the trailing face 56 of the wing 49.

Fig.8 shows another rotor 4 with hydraulically operated wings 57. In this case though the radially outer edge face 52 of the metal wing 57 has mounted in a trailing side recess 58, a flexible plastics sealing element 59 and the wing 57 has an enlarged width base 60 which abuts stop shoulders 61 at the mouth 62 of the wing mounting slot 50 so as to limit the radially outward movement of the wing 57 and hold the metal outer edge face 52 clear of the inner casing 2 whilst permitting sealing contact therewith by the sealing element 59 thereby preventing undue wear in the motor and allowing the use of harder metals e.g. high performance steels, in the wings, though' hard plastics e.g. polyimide or phenolic resins e.g. phenol formaldehyde resins such as those available under the Trade Mark TUFNOL, may also be used'for the wings. The sealing elements may be made of any suitable plastics material including for example high temperature nitrile rubber or PTFE (polytetrafluoroethylene) .

It will be appreciated that, with the use of a suitable strainer 63 (as shown in Figs 6 and 8 but omitted from Fig.7 for clarity) lining the internal conduit 32 of the rotor 4, it is possible to use fluids such as drilling muds containing fibres and/or other lost circulation material for "sealing" porous strata against absorption of drilling mud, without the risk of such materials interfering with the operation of the motor.

It will also be understood that various modifications may be made to the the abovedescribed embodiments without departing from the scope of the present invention. Thus for example in the motor of Fig.l, the inlet and outlet apertures 19,20 of the inner casing are desirably minimised in size in order to reduce wear on the wings 15. Also there could be used an integrally formed casing with suitable inlet and outlet conduit means 19a,20a_ formed therein, instead of separately formed inner and outer casings 2,1 which define longitudinally spaced annular inlet and outlet conduit means 19a,20a therein either side of the annular wall 21. The latter arrangement is however preferred though from the point of view of manufacturing convenience and also because it helps to maximize the cross-sectional area of the inlet and outlet conduits 19a,20a thereby reducing resistance to fluid flow through the motor and facilitating maximum fluid flow through the motor thereby maximizing torque etc. This in turn helps to minimize the overall diameter of the motor required to achieve a given torque which is particularly significant in the context of the small diameter of boreholes and the like in which the motor may be used. In order further to simplify manufacture of the motor, the radially extending wall means 3 are also conveniently formed separately and connected to the inner casing by any suitable means preferably releasable ones e.g. bolts, which also allows for replacement thereof when required e.g. as a result of wear. Where the casing is in two parts as shown in Fig.l and an annular wall 21 is used to separate the inlet and outlet conduits 19a,20a, the wall 21 is desirably fixed securely to both the inner and outer casings 2,1 e.g. using bolts or radially extending pins, so as to prevent relative rotation therebetween and absorb the reactive forces during running of the motor. As shown in Fig.l the wall means 21 is desirably provided with suitable high performance seals 64 e.g. high temperature silicon rubber seals. As indicated above various numbers of radially extending walls 3 and wings 15 may be used. Advantageously at least two wings are used for each wall so that there are usually at least two wings 15 between successive walls 3. This increases sealing between the inlets and outlets 19,20 and hence maximizes the torque of the motor. In order to increase the maximum operating speed of the motor, the wings should desirably be made as light as possible to minimize their inertia and the driving force on them maximized (e.g. by using hydraulically operated drive means as described above) .

The motors of the invention may be used for various purposes with various working fluids including gases such as compressed air. As noted above though the motors of the invention are particularly suitable for use in downhole applications such as drilling and coreing and the present invention includes with its scope drilling and coreing apparatus wherein the motor is a motor of the present invention, as well as methods of driving drilling and coring apparatus using a motor of the present invention.

Claims

1. A motor suitable for use in down-hole drilling applications, characterised in that said motor is a wing motor and comprises a generally tubular casing (1,2) ahd a rotor (4) mounted for rotation within said casing (1,2) and substantially radially spaced therefrom so as to define a chamber (18) therebetween, said casing (1,2) being provided with angularly spaced apart inlet means (19) and outlet means (20) for ingress of pressurised working fluid from inlet conduit means (19a) in said casing (1,2) into said chamber (18) and egress of said fluid from within said chamber, to outlet conduit means (20a) separated from said inlet conduit means (18) by wall means (21) , in use of the motor, said casing (2) having generally radially extending wall means (3) extending,, substantially into contact with said rotor (4) at an angular position between said outlet means (20) and said inlet means (19) , said rotor (4) having a plurality of angularly spaced apart wing means (15) , one of said radially extending walls means (3) and said wing means (15) being displacable from a generally radially projecting configuration in substantially sealing engagement with said rotor (4) or said casing (1,2), respectively, to a generally retracted configuration, when traversing the other of said radially extending wall means (3) and said wing means (15) , said wing means (15) and inlet and outlet means (19,20) being formed and arranged and relatively angularly disposed so that, in use of said motor, a flow of pressurised fluid into said chamber (18) acts against an upstream side (15c) of a first said wing means (15') so as to rotate said rotor (4) while venting fluid from its downstream side (15e) until said wing means (15') traverses said outlet means (20) and a second said wing means (15") traverses the inlet means (19) whereupon said process is repeated.

2. A motor according to claim 1 wherein said casing comprises a generally tubular outer casing (1) and a generally tubular inner casing (2) and said inlet and outlet conduit means (19a,20a) are defined between said inner and outer casings (2,1).

3. A motor according to claim 2 wherein said wall means between said inlet and outlet conduit means (19a,20a) comprises an annular wall (21) , said inlet and outlet conduit means comprising longitudinally spaced apart annular passage means (19a.,20a) at opposite sides of said annular wall (21) .

4. A motor according to any one of claims 1 to 3 wherein said wing means (15) of the rotor (4) are formed and arranged so as to be displacable from a generally radially projecting configuration in substantially sealing engagement with the inner^' casing (2) , to a generally retracted configuration when traversing the radially extending wall means (3) .

5. A motor according to claim 4 wherein said wing means (15) are formed and arranged so as to be resiliently angularly deflectable between said generally radially projecting configuration and a said substantially retracted configuration in which said wing means (15) extends generally circumferentially of the rotor (4) .

6. A motor according to claim 5 wherein said wing means

(15) are hingedly mounted on said rotor (4) .

7. A motor according to claim 4 wherein said wing means (15) are formed and arranged so as to be generally radially displacable between said generally radially projecting and substantially retracted configurations.

8. A motor according to claim 7 wherein said wing means (39) are provided with resilient biasing means (44) formed and arranged for acting between the rotor (4) and the wing means (39) so as to urge said wing means (39) radially outwardly.

9. A motor according to claim 7 or claim 8 wherein each said wing means (39) is mounted in a generally radially extending recess (41) so as to be slidably displacable therein between said radially extending and retracted configurations.

10. A motor according to claim 9 wherein each said wing means (49) is provided at a radially inward side (43) with hydraulically operated drive means (51) , for urging said wing means (49) towards its radially extending configuration, in use of the motor, said rotor (4) being provided with internal conduit means (32) connected (50) to said recess for supplying, in use of the motor, high pressure working fluid to said drive means (51) .

11. A motor according to claim 10 wherein said drive means comprises a piston means (51) mounted in a cylinder bore means (50) connecting said recess (41) to said internal conduit means (32) .

12. A motor according to any one of claims 1 to 11 wherein are provided at least four said radially extending wall means (3) and at least eight wing means (39) .

13. Apparatus for use in drilling and/or coring having a downhole motor characterised in that said motor comprises a motor according to any one of claims 1 to 12.