HYDRAULIC MOTOR

Abstract: A high torque, low speed hydraulic motor with radial slots (14) formed in the inner face of a housing forming working chambers; lobed rotors (22) have lobes (23) meshing with each chamber in turn as a drive element, on which the rotors (22) are rotatably mounted, rotates; the lobes having provision to admit through a port (32) pressurised hydraulic fluid and to discharge via a groove (33) in each lobe spent hydraulic fluid from the working chambers during the various stages of mesh.

Description: HYDRAULIC MOTOR FIELD OF INVENTION This invention relates to hydraulic motors which derive their output power from the flow of fluid under pressure to the rotating parts. The invention will be described in relation to a hydraulic motor of the kind that may be installed as a down-hole drill motor at the lower end of a long drill string and be driven by the pressurised slurry normally used for drill bit lubrication and cooling. However, it is to be understood that the invention is not limited thereto as the motor (albeit with or without minor modifications) may be used with general purpose hydrostatic transmission systems as a high torque/slow speed motor. BACKGROUND ART Down-hole drill motors are known in various forms, the most familiar and widely known of which, is the turbo¬ drill. As the name implies, the turbo-drill is based on the multi-stage turbine principle with drilling mud as the working fluid. Other positive displacement hydraulic motors used commercially, or which may still be at the experimental stage, include eccentric lobed rotor (as in the mono pump) and flexible vane types. Most down-hole turbo-drills or positive displacement motors derive their high torque/slow speed characteristic from a gradual pressure drop of the motive fluid over a relatively large axial length. DISCLOSURE OF INVENTION It is an object of the invention to provide a hydraulic motor having high torque/slow speed characteristics within a relatively short axial dimension, making it particularly suitable for directional drilling, together with simplicity and ruggedness of design as will be suitable for bore or well applications. According to the invention there is provided a hydraulic motor comprising a body defining a chamber that has a plurality of cylinders formed therein, a drive element within the chamber adapted to be coupled to an output shaft, a multi-lobed rotor mounted on the drive element with the lobes adapted to co-operate sequentially with the cylinders, a passageway in each lobe through which fluid applied to the interior of the rotor is directed to the cylinder during pre-deter ined locations of each lobe whereby the lobe is forced from the cylinder and the force so produced is transferred as torque to the drive element. Preferably, there are three rotors each with three lobes and ten cylinders but the prinicple can equally be applied to a three rotor/three lobe, six, eight or nine cylinder configuration. The motor is capable of staged assembly whereby each individual power module or motor may be connected in line with one or more further modules to increase the final output shaft power. In a preferred form of the invention, the working fluid is the pressurized mud slurry used for flushing of drilling debris and lubrication and cooling of the drill bit at the end of a drill string. The working fluid passes through each stage in turn and a portion of the total flow is extracted at each intermediate stage to provide motive power for the module of that stage. The motor modules are, in effect, operating hydraulically in parallel and mechanically in series. BRIEF DESCRIPTION OF THE DRAWINGS In order that the invention may be more readily understood and put into practical effect, reference will now be made to the accompanying drawings in which: Fig. 1 is a cross-sectional view of a single stage hydraulic motor according to one embodiment of the invention. Fig. 2 is a cross-sectional view of a second stage or module hydraulic motor adapted to be connected to the first stage shown in Fig. 1, Fig. 3 is a diagrammatic representation of the porting arrangement by which fluid is transmitted to and discharged from the cylinders of the hydraulic motor shown in Fig. 1, Fig. 4 is a diagrammatic representation of the porting arrangement by which fluid is transmitted to and discharged from the cylinders of the motor shown in Fig. 2, Fig. 5 is an exploded view of the central portion of the motor shown in Fig. 1, and. Fig. 6 is a schematic view of a down-hole drill string, motor and drill bit arrangement. The hydraulic motors shown in Figs 1 and 2 each include a hollow body 10 that is closed by a non-drive end housing 12 and a drive end housing 13 all of which are held in position by bolts 11. A plurality of radial slots or recesses 14 formed in the inner face of the body 10 constitute the working cylinders of the motor (see Fig. 3). The first and second stages are substantially similar and will, when appropriate, be described together. The end housings 12 and 13 have taper roller bearings 16, 17 which support a drive element 15 in the chamber defined by the body 10. Oil or grease is sealed within the bearings 16, 17 by polymer seal plates 18 which act against mating faces of the drive element or rotor 15 and by plates 18a sealing against locking rings 20 attached to the non- drive end stub shafts 24 (Fig. 2) and 24a (Fig. 1) and to the drive-end stub shafts 26 (Fig 2) and 26a (Fig. 1). As shown in Fig. 2, sealing pressure is provided by compression springs 40, 41 which act against seal plates 18 and 18a respectively. The drive element 15 (see Fig. 2) consists of two flanged components 19, 19a that are connected together by three equally spaced circular, hollow pins 21. Each pin 21 carries a rotor 22 having three lobes 23 free to rotate on the pin 21. The drive element for the second stage motors also has three transfer tubes 50 between the flange components 19, 19a (see Fig. 4) and the drive element for the first stage has three rotor torsion pins 51 between the flange components 19, 19a (see Fig. 3). As can be see in Figs. 3 and 4, the rotor lobes 23 engage each cylinder 14 in turn as the drive element 15 and rotors 22 turn (in opposite directions) thereby forming a sealed chamber to which the pressurised fluid is admitted. The porting arrangement and method of transfer by which fluid is transmitted to and discharged from the cylinders 14 is shown diagramatically in Fig. 3 for the first stage motor of Fig. 1 and in Fig. 4 for the second stage motor of Fig. 2. High pressure (i.e. inlet) fluid is indicated by solid lines and low pressure (i.e. discharge) fluid by broken lines. The non-drive end flange component 19 has a hollow stub shaft 24 (Fig 2), 24a (Fig. 1) and a - b pressurised fluid passageway 25 (Fig. 2), 25a (Fig. 1) through which the driving fluid is introduced into the motors of Figs. 1 and 2 in the direction of arrows A. The drive end flange component 19a has a hollow stub shaft 26 (Fig. 2) having a passageway 27 (Fig. 2) through which a portion of the pressurised driving fluid is discharged in the case of the Fig. 2 motor in the direction of arrows B to the motor of Fig. 1. An annular connector flange 28 is used to join the first and second stages and the drive end stub shaft 26 of one unit receives the non-drive end shaft 24a of the next unit with a seal 29 therebetween. Each rotor pin 21 has a port slot 31 which overlaps, in turn, with three corresponding ports 32 in the rotor • 22. The rotor ports 32 provide a passageway for fluid under pressure through each lobe 23 into the cylinder chambers 14 to provide the power stroke by forcing the lobe from the cylinder. The rotor ports 32 open at the top dead centre of each lobe 23 in a cylinder 14 and close at the point of departure of the lobe from the cylinder. The force produced on the rotor 21 is transferred as torque to the drive element 15 and to the final output shaft (not shown) of the motor. During operation, the body of the motor is full of fluid at discharge pressure. When a lobe 23 is entering a cylinder 14, the fluid is displaced by an axial rectangular groove 33 on the periphery of each lobe 23 which breaks the seal over that segment of the working cycle. In a multi¬ stage motor, discharge fluid is then released from the first stage by passageway 34 in the non-drive end plate 12 and passageway 35 in the drive end plate 13, in the direction of arrows D. If the motor is the final or only stage as is the case with the Fig. 1 motor, all pressure fluid is translated into rotational energy through the drive element 15. Spent fluid is discharged into the body 10 and thence through the passageway 27a to the drill bit (arrows C in Figs 1 and 3). The use of an hydraulic motor of the invention as a down-hole drill motor is shown in Fig. 5 where the first motor unit 60 is bolted direct to- the lower flange of the drill string of pipes 61 which provide the inlet supply fluid from supply line 62. The outward shaft of the final motor unit is connected direct to the drill bit 64 or through an intermediate coupling. Thus, it can be seen that the hydraulic motor derives its output power from a flow of fluid supplied under pressure to the rotating parts. Although the motor is designed principally as a down the hole drill motor for deep wells it may also be applied (with suitable modifications) to general purpose hydrostatic transmission systems as a high torque/slow speed motor. The motor can be readily adapted for 'staged' assembly whereby each individual motor as described above may be connected in line with one or more further motors to increase the final output shaft power. When used as a drill motor, the working fluid is pressurised mud slurry as used conventionally for flushing, lubrication and cooling a drill bit, which passes through each stage in turn. A portion of the total flow is extracted at each motor stage to provide motive power for that drive element. After discharge from the working stroke the fluid is released from the motor body to provide flushing, lubrication and cooling for the drill bit attached to the motor output shaft. Various modifications may be made in details of design and construction without departing from the scope and ambit of the invention. For example, when adapted for general use, the hydraulic motor is not subjected to the stringent diametral constraints of a down the hole drill motor and thus the inlet and outlet connections for the working fluid (such as hydraulic oil) could be located in one plate or casting at the non-drive end of the motor.

Claims: CLAIMS 1. An hydraulic motor comprising a body defining a chamber that has a plurality of cylinders formed therein, a drive element whithin the chamber adapted to be coupled to an output shaft, a multi-lobed rotor mounted on the drive element with the lobes adapted to co-operate sequentially with the cylinders, a passageway in each lobe through which fluid applied to the interior of the rotor is directed to the cylinder during pre-determined locations of each lobe whereby the lobe is forced from the cylinder and the force so produced is transferred as torque to the drive element. 2. A motor as claimed in claim 1 wherein the drive element comprises a pair of spaced apart flange means that are connected together by a plurality of hollow pins and wherein a multi-lobed rotor is mounted on each hollow pin. 3. A motor as claimed in claim 2 wherein one of said flange means is a drive end flange means and the other is a non-drive end flange means and wherein the non-drive end flange means has a hollow stub shaft through which the driving fluid is introduced into the motor and the drive end flange means is connected to the output shaft. 4. A motor as claimed in claim 3 wherein the motor is a multi-stage motor in which the drive end flange means of one motor is adapted to be coupled to the non-drive end flange means of a similar hydraulic motor and has a hollow stub shaft through which driving fluid is discharged into the said similar hydraulic motor. 5. A motor as claimed in claim 3 wherein the drive end flange has a hollow stub shaft through which all discharge fluid is led to a drill bit. 6. A motor as claimed in claim 3 wherein each rotor hollow pin has a port which overlaps, in turn, with the passageway in the respective lobes whereby the working fluid is directed from the non-drive end flange into the hollow pins and through the port in the pins into the lobes and thence to the respective cylinder. 7. A motor as claimed in claim 6 wherein each lobe has an axial groove on its periphery to break the seal between the lobe and its cylinder at that segment of the movement of the lobe. 8. An hydraulic motor assembly comprising a first motor substantially as claimed in claim 1 and a second motor substantially as claimed in claim 1 and wherein the working fluid is passed through each motor in turn with a portion of the fluid flow being extracted at each motor.

Inventors: BURNS ALAN ROBERT, RIGBY ROBERT WILLIAM, BURNS, ALAN, ROBERT, RIGBY, ROBERT, WILLIAM
Applicants: TENNYSON HOLDINGS LTD, TENNYSON HOLDINGS LTD.
Application year: 1986
Main classification: F01C1
IPC codes: F01B13, F01C1, F03C1, F03C2