Coupling device for converting mechanical torque into hydraulic pressure for exerting radial thrusting force on drive wheels in a pulling tool in a well

BACKGROUND OF THE INVENTION

The present invention concerns a conversion device for converting mechanical torque to hydraulic pressure in a liquid.

More specifically, it concerns a device of the kind to be used in a mechanical conveyor/ pulling tool, where the purpose of the device is to transform a mechanical torque to hydraulic pressure in a liquid, which pressure in turn can be used to exert a radial thrusting force on drive wheels against the wall of a bore.

During maintenance or inspection of pipes, pipelines and wellbores, e.g. for oil, gas or water production, it is frequently necessary to use a conveyor/ pulling tool in order to enter sufficiently deep into the pipes or bores with miscellaneous tools and equipment for maintenance or inspections.

Particularly in oil and gas wells having a lot of advanced equipment for optimal oil production, advanced maintenance operations are now being performed. Such operations require reliable and cost efficient tool carriers. Today, conveyor/ pulling tools of various constructions are used. The most common are electro-hydraulic apparatuses where the propulsion mechanism on the transporting device is driven by hydraulic motors located directly within the wheels. Alternatively, the power is transmitted through gear systems of various constructions.

In pipes or wellbores having a small diameter the dimensions of wheels and motors are very limited. This leads to small dimensions in the components, and consequently large hydraulic flow losses and less robust constructions.

In order to obtain sufficient force and flexibility, hydraulic pressure in a liquid is frequently used to provide sufficient friction through thrusting force on wheels or belts contacting the pipe or bore wall.

In drive mechanisms having direct mechanical gear transmissions between the motor and wheels/belts, a conversion device is necessary for regulating the hydraulic liquid pressure providing thrusting force on the drive wheels/belts contacting the bore wall.

The thrusting force on the drive wheels or belts contacting the pipe or bore wall must be adjustable depending on applied mechanical torque from the motor, such that a sufficient friction between wheels/belts and the bore wall is achieved.

SUMMARY OF THE INVENTION

With the present invention a coupling device is disclosed, which in a functional and practical feasible way provides a relation between mechanical torque and hydraulic liquid pressure activating the drive wheels against the bore wall, so that the thrusting force on the drive wheels against the bore wall is adjusted proportional to the mechanical torque.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, an example of a preferred embodiment is disclosed with reference to the accompanying drawings, in which:

Fig 1 shows a wheeled modular conveyor/ pulling tool in a wellbore, Fig 2 shows a mechanical gear transmission mechanism for transmission of torque to drive wheels

Fig 3 is a cross section of the coupling device

Fig 4 shows a detail of the coupling device

Fig 5 shows the principle of the valve function for hydraulic pressure on the thrusting mechanism for drive wheels or belts

DETAILED DESCRIPTION OF THE INVENTION

Reference is first made to figure 1 , in which reference numeral 1 refers to a pipe or wellbore, e.g. for production or transport of oil, gas or water. A conveyor/ pulling tool is positioned within the pipe or wellbore 1. The conveyor/ pulling tool comprises drive modules 6, having drive wheels 4 connected to levers 5 for radial displacement of the wheels 4 towards the pipe or bore wall. The conveyor/ pulling tool is powered by an electromotor 3 supplied with power and signals through cable 7.

A mechanical coupler 2 is disposed between the motor 3 and drive modules 6. The coupler 2 constitutes the invention, and will be described in greater detail in the following.

Figure 2 and figure 5 shows the main principle for the mechanical power transmission in the drive module. From the motor 3, torque is transmitted through the mechanical coupling device 2, further through the gears 8, shaft 9, bevel gear 35 and gears 36 to the drive wheels 4.

The drive wheels 4 are forced towards the wall of the pipe or wellbore by means of the lever 5 and cogged hydraulic pistons 31 engaging the gear 32 disposed on the lever 5.

The function of the coupling device 2 is to control the hydraulic pressure on the pistons 31 to be proportional to the torque from the motor 3. At increasing torque, the hydraulic pressure increases, whereby the drive wheels 4 are forced harder against the wall of the wellbore 1. This functionality is necessary in order for the conveyor/ pulling tool to be able to adapt to, and pass, different diameters in the wellbore.

Fig 3 shows a cross section through the coupling device 2 having an incoming shaft 12 and an outgoing shaft 15. A spring 20 thrusts an adapter 17 towards a part 33 of the outgoing shaft 15, having an extended diameter.

Fig 4 shows incoming shaft 12 supported in the housing 11 by ball bearing 13. The incoming shaft 12 having tapered surfaces 25 engaging rollers 24 rotatable about bolts 34 in part 33 of the outgoing shaft 15. The outgoing shaft 15 is supported by ball bearing 14. The adapter 17 from fig 3 is provided with splines 23 engaging corresponding splines in the housing 11 , so that the adapter 17 may be displaced in the axial direction only. The spring 20 thrusts the adapter 17 towards the bearing 14 and the part 33 of the outgoing shaft 15 so that the rollers 24 are always in engagement with the tapered surfaces 25.

When a torque 10 is applied to the incoming shaft 12, a relative rotation between the incoming shaft 12 and the outgoings shaft 15 will occur, depending on the thrust from spring 20. This rotation is due to the rollers 24 moving on the tapered surfaces 25. This rotation causes an axial displacement of the adapter 17 and further of the shaft 21 engaging the adapter 17 at the surface 22.

Referring to fig 5, the displacement 29 of the shaft 21 is transmitted to a spring 26 within the valve unit 16. The force from the spring 26 thrusts the ball 27against the seat 28, whereby the hydraulic pressure on the pistons 31 are increased. The increased pressure in the pistons 31 is transmitted to the lever 5 through gear 32 engaging cogging on pistons 31.