Claims:CLAIMS
We Claim:
1. An integrated rotary drive mechanism (100) for a drill rig, the integrated rotary drive mechanism (100) comprising:
a radial piston motor (20) including a housing (12) having a cam profile (13), a cylinder block (16) having a plurality of beam assemblies (14) radially disposed therein, wherein the inner surface of cylinder block (16) provides a bearing surface for the plurality of beam assemblies (14);
a hollow shaft (60) rotatably received in the cylinder block (16) through a spline shaft coupling; the hollow shaft (60) having a lower end (60b) connected to a drilling pipe that is further connected to a drill hammer, and an upper end (60a) connected to a air supply for supplying compressed air needed for drilling hammer and for removing dust /mud during drilling operation;
a pair of tapered roller bearings (26) mounted below the radial piston motor (20) for supporting the hollow shaft (60), the pair of tapered roller bearings (26) housed in a bearing support (40);
a pneumatic seal (22) with a seal carrier (24), fitted on the hollow shaft (60) above the radial piston motor (20), to avoid entry of dust and air into the radial piston motor (20), wherein the seal carrier (24) is dismantled and assembled while replacing the pneumatic seal (22) after service life; and
an oil seal (9) fitted on the hollow shaft (60) below the bearing support (40 to avoid leakage of motor oil and to avoid the entry of dust/ mud into the radial piston motor (20);
2. The integrated rotary drive mechanism (100) as claimed in claim 1, wherein the radial piston motor (20) is a high torque low speed motor designed to handle vibrations during drilling operation.
3. The integrated rotary drive mechanism (100) as claimed in claim 1, wherein the pneumatic seal (22) is an elastomeric seal.
4. The integrated rotary drive mechanism (100) as claimed in claim 1, wherein the pair of tapered roller bearings (26) are capable of handling up to 20000 kg axial load and up to 5000 kg radial load during drilling operation.
Dated this 23rd day of October, 2019

Ashwini Kelkar
(Agent for Applicant)
IN-PA/2461

, Description:ROTARY DRIVE MECHANISM FOR DRILL RIG
Field of the invention:
The invention generally relates to a drill rig and more particularly it relates to a rotary drive mounted at the top of the drill rig for rotating drill pipes and drill hammers.
Background of the invention:
Drill Rigs are used to create holes in the earth subsurface. A drill rig for drilling a hole in the ground including a mast having railing on which rotary drive reciprocates.
Figure 1 shows rotary drive system (10) of existing drill rigs. The rotary drive (10) comprises of an axial piston motor (1) coupled with a speed reduction gearbox (2) to reduce the speed in the ratio 3:1.The torque up to 425 kg-m is then transferred to a hollow shaft (3). Multiple bearings (4) are used to take the load exerted by axial piston motor (1) and load generated during drilling operation. When the hydraulic oil is supplied to rotary drive, it rotates and transfers torque to the drill pipes and drill hammers coupled to the hollow shaft (3). Seals are used to avoid mixing of air and gear box oil. Multiple drill pipes are coupled or decoupled from the drive shaft to drill water well holes up to a depth 2000 ft. A drill hammer is connected at the end of the drill pipes to provide impact, which facilitates drilling of hard rocks and generates vibration. Compressed Air at 30 Bar to 40 Bar is passed through the hollow shaft (3) to feed the drill pipes and drill hammer to remove soil and drill hard rocks from the earth sub surface during operation. The efficiency of the current system (10) is less (94%) due to integration of gearbox (2) with axial piston motor (1). (Motor efficiency 97% X gear box efficiency 97%). Secondly, the axial piston motor (1) cannot generate maximum torque at low speed (RPM<1).
Accordingly, there exists a need for a rotary drive mechanism for a drill rig which overcomes abovementioned drawbacks.
Objects of the invention:
An object of the present invention is to provide a rotary drive mechanism for a drill rig to provide maximum torque at low speed.
Another object of the present invention is to provide a rotary drive mechanism for a drill rig, with reduced number of parts improving serviceability and maintenance.
Still another object of the present invention is to eliminate the use of axial piston motor and gear box in a rotary drive system for drill rig.
Summary of the invention:
Accordingly, the present invention provides an integrated rotary drive mechanism for a drill rig for drilling of bore well. The present invention eliminates the use of axial piston motor along with speed reduction gearbox in the drill head drive. The integrated rotary drive mechanism of present invention comprises of a radial piston motor receiving a hollow shaft supported by a bearing support to meet the load bearing capacity and other requirements for earth drilling. The radial piston motor is a high torque low speed motor designed to handle vibrations during drilling operation and it consists of a housing having a cam profile and a cylinder block having a plurality of beam assemblies radially disposed therein, wherein the inner surface of cylinder block provides a bearing surface for the plurality of reciprocating beam assemblies. A hollow shaft is rotatably received in the cylinder block through a spline shaft coupling. The hollow shaft is having a lower end connected to a drilling pipe that is further connected to a drill hammer, and the upper end connected to a air supply for supplying compressed air needed for drilling hammer and for removing dust /mud during drilling operation. A pair of tapered roller bearings is mounted below the radial piston motor for supporting the hollow shaft. The pair of tapered roller bearings is housed in a bearing support and is capable of handling up to 20000 kg axial load and up to 5000 kg radial load during drilling operation. A pneumatic seal with a seal carrier is fitted on the hollow shaft above the radial piston motor, to avoid entry of dust and air into the radial piston motor, wherein the seal carrier is dismantled and assembled while replacing the pneumatic seal after service life; and an oil seal is fitted on the hollow shaft below the bearing support to avoid the leakage of motor oil and to avoid the entry of dust/ mud into the radial piston motor.
Brief description of the drawings:
The objects and advantages of the present invention will become apparent when the disclosure is read in conjunction with the following figures, wherein
figure 1 shows a detailed cross sectional view of a rotary drive mechanism for a drill rig, in accordance with the prior art;
figure 2 shows a rotary drive mechanism for a drill rig, in accordance with the present invention;
figure 3 shows a detailed cross sectional view of a rotary drive mechanism for a drill rig, in accordance with the present invention; and
figure 4 shows a detailed cross sectional view of internal parts of radial piston motor in the rotary drive mechanism, in accordance with the present invention.
Detailed description of the embodiments:
The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiments.
The present invention provides a rotary drive mechanism for a drill rig. This is a direct drive mechanism in which the axial piston motor and speed reduction gearbox of the prior art is replaced by a high torque low speed radial piston motor with some modifications of internal parts to achieve the output. The internal rotating parts of the radial piston motor are modified to handle heavy vibrations generated during drilling operation. In present invention, the radial piston motor, a bearing support and a hollow shaft are integrated as one piece to meet the load bearing capacity and are directly coupled to drilling pipes for drilling operation. One end of the hollow shaft is connected to the air side and the other end is connected to the drilling pipe which in turn is connected to a drill hammer. When oil is supplied to the radial piston motor, the torque is transferred to the hollow shaft through the splines. Due to elimination of speed reduction gear box, the mechanism provides high efficiency and the direct drive delivers full torque even at low speed (425 kg-m at 1 RPM).
The present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures. These reference numbers are shown in bracket in the following description. Table 1 below enlists all the reference numerals along with respective component names:
Table 1
Ref No Component Ref No. Component
12 Motor housing 24 Seal carrier
13 Cam profile 26 Tapered roller bearings
14 Beam assembly 30 Oil seals
16 Cylinder Block 40 Bearing support
18 Bearing surface 60 Hollow shaft
20 Radial piston motor 60a Upper end of hollow shaft
22 Pneumatic seal 60b Lower end of hollow shaft

Referring to figures 2 to 4, a rotary drive mechanism (100) (hereinafter referred as “the mechanism (100)”) for a drill rig in accordance with the present invention is disclosed. The drill rig is used for drilling wellbore. The mechanism (100) comprises of a radial piston motor (20) including a housing (12) having a cam profile (13), a cylinder block (16) having a plurality of beam assemblies (14) radially disposed therein. The inner surface (18) of the cylinder block (16) is modified to handle vibration generated during drilling operations. Normally, wear plates are clamped on either sides of the beam assembly, to act as a bearing surface. Usually the Wear plates dislodge when the motor is subjected to vibration during operation since they are just clamped to the cylinder block (16). In the present invention, the wear plates are eliminated by reducing the slot width of cylinder block (16) by double the width of wear plate, to accommodate the reciprocating beam assembly (14) therein. The inner surface (18) of the cylinder block (16) provides a bearing surface for the plurality of beam assemblies (14). In an embodiment, the radial piston motor (20) is a high torque low speed motor designed to handle vibrations during drilling operation.
A hollow shaft (60) is rotatably received in the cylinder block (16) through a spline shaft coupling. The hollow shaft (60) is having a lower end (60b) connected to a drilling pipe that is further connected to a drill hammer, and the upper end (60a) connected to air supply for supplying compressed air needed for drilling hammer and for removing dust and mud during drilling operation.
A pair of tapered roller bearings (26) housed in a bearing support (40) is mounted below the radial piston motor (20) for supporting the hollow shaft (60). The pair of tapered roller bearings (26) is capable of handling up to 20000 kg axial load and up to 5000 kg radial load during drilling operation. A pneumatic seal (22) with a seal carrier (24) is fitted on the hollow shaft (60) above the radial piston motor (20) to avoid entry of dust and air into the radial piston motor (20), wherein the seal carrier (24) can be dismantled and assembled while replacing the pneumatic seal (22) after service life. In an embodiment, the pneumatic seal (22) is an elastomeric seal. An oil seal (9) is fitted on the hollow shaft (60) below the bearing support (40) to avoid leakage of motor oil and to avoid the entry of dust/ mud into the radial piston motor (20).
In this invention, both axial piston motor and speed reduction gear box are eliminated and the torque required for drilling is generated using direct drive high torque low speed radial piston motor (20). Internal parts of radial piston motor are modified to handle vibrations generated during drilling operations. Arrangements are made to integrate the parts of radial piston motor (20), bearing and hollow shaft to meet the load bearing capacity other requirements for earth drilling. This arrangement provides high efficiency as the speed reduction gear box is removed and direct drive is used which delivers full torque even at low speed (425 kg-m at 1 RPM). The reduced number of components compared to current solution improves serviceability and maintenance.
Advantages of the invention:
• The mechanism (100) of the present invention provides a direct drive for the drilling pipes and hence higher efficiency.
• Improved serviceability and maintenance as the number of parts is reduced.
• The mechanism (100) is designed to suit the drilling application which requires passage for air supply and the internal parts are modified to handle high vibration and load.
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, and to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but such omissions and substitutions are intended to cover the application or implementation without departing from the scope of the claims of the present invention.