INVERTED BALL SCREW ACTUATOR

Abstract

The present invention relates to linear actuators and, in particular, to powered linear actuator for converting rotational movement into linear movement, and vice versa. The present disclosure has use to applications requiring high performance, high force and speed. This invention is performing both at surface, subsurface and subsea with purpose to replace hydraulic cylinders

Claims

1. Linear actuator for providing rotational movement into linear movement and vice versa, the linear actuator comprising: - an outer ball lead-screw (4) with internal helical ball rolling grooves - an inner ball lead-screw body (5) having outer helical ball rolling grooves and deflector circuit - the outer ball lead-screw (4) is rotated to laterally move the inner lead-screw body (5) through a plurality of balls in rolling contact with the outer ball lead-screw (4) and the inner ball lead-screw body (5) to transfer the load and to achieve lateral movement of the piston rod (12) - an inner ball lead-screw body (5) with deflector channel (17) between two helical ball rolling circuits communicating with each other as the recirculation groove gradually slopes into a diameter slightly larger than the ball before entering into the ball deflector channel (17) where the deflector groove is deep enough for the bearing balls to pass unimpeded over the land between the adjacent grooves of the outer lead screw (4) - the number of helical ball rolling surfaces on the outer ball lead-screw (4) is giving the lateral stroke of the piston rod(12) Characterised by; - the outer ball lead-screw (12) rotates and is threadingly engaged with the inner lead screw body (5) through a plurality of balls (16) - the inner lead-screw body (5) is fixed to the rod (12) and is moved laterally by the plurality of balls (16) between the outer-lead scew (4) and inner lead-screw body (5) - a deflector channel between each ball recirculation circuit on inner lead-screw body (5) - the deflector channel is formed in a way that prevent the balls to fail out of the deflector channel when passing over the land between the adjacent grooves of the outer-lead screw (4) - at least one protruding rod (12).

2. Linear actuator according to claim 1, whereas a piston rod (12) is connected to the inner lead-screw (5) and outer lead-screw (4) through a plurality of balls (16) for transferring the lateral movement into rotational movement.

3. Linear actuator according to any of claims 1 to 2 wherein a plurality of rolling balls (16) is running among first and second grooves of the outer lead-screw and the circulating channels in the inner lead-screw.

4. Linear actuator according to any of claims 1 to 3, wherein the outer lead-screw (4) have maximum groove depth is slightly less than the diameter of the balls.

5. Linear actuator according to claim 1, 2 and 4, whereas the piston rod (12) is prevented from rotating.

6. Linear actuator according to claim 1, wherein the said apparatus having a spring system for moving the rod laterally in a said direction.

7. Linear actuator according to claim 1, wherein the end plates (2) (10) and housing (3) supports the outer lead-screw, laterally and radially.

8. Linear actuator according to claim 1 and 7, wherein the lateral force is provided with rotational motion from an electric motor.

9. Linear actuator according to claim 1 whereas the drive unit have at least one electrical connector comprises inductive couplings for transmission of power and data.

10. Linear actuator according to claim 1, wherein the drive unit have at least one electrical connector is a wet-mate connector.

11. Linear actuator according to claim 1, wherein the one of the end caps (4) includes a brake gear, or both function.

12. Linear actuator according to claim 9. wherein at least one connector comprises a plurality of electrical connectors.

13. Linear actuator according to claim 1, 9 and 10, wherein the outer lead-screw is supported laterally and radially and is connected to a mechanical override whereas the rotational energy in form of torque can be provided by a remote operated vehicle (ROV) or a hand-held tool.

14. Linear actuator according to claim 1, 9 to 13. wherein the apparatus can be operated directly with an ROV.

15. Linear actuator according to claim 1 to 13, wherein the housing (3) is oil filled and protected towards ambient pressure from the surrounding.

16. Linear actuator according to any of claims 1-15, further compromising a mechanical interface formed as a bucket coupling and a drive shaft.

17. Linear actuator according to claim 1 further comprising electronic limit control that senses motor current and provides end-of-stroke shut off and mid-stroke thrust shut-off.

Description

[0033] FIG. 1 is an illustration of an example of an inverted ball screw actuator device packed inside a housing (3) with the piston rod (12) retracted into the housing (3) according to an embodiment of the disclosure;

[0034] FIG. 2 is a side view of an example of an inverted ball screw actuator device packed inside a motor housing (3) with the piston rod (12) retracted into the housing (3) according to an embodiment of the disclosure:

[0035] FIG. 3 is a side view of an example of an inverted ball screw actuator device packed inside a motor housing (3) with the piston rod (12) fully extended out from the housing (3) according to an embodiment of the disclosure;

[0036] FIG. 4 is an illustration of an example of an inverted ball screw actuator device packed inside a housing (3) showing the drive side (10) of the piston rod (12) according to an embodiment of the disclosure:

[0037] FIG. 5 is a cross sectional illustration of an inverted ball screw actuator device showing an example of a ball screw arrangement, the piston rod (12) and drive side (10) to an embodiment of the disclosure:

[0038] FIG. 6 shows the inverted ball screw recirculation circuits (17) also referred to as cylinder piston device (5), the inverted ball screw actuator device drive side sealing device (7) and piston rod (12) sealing device (2), as an example of an embodiment of the disclosure;

[0039] FIG. 7 shows the cross-sectional illustration of an inverted ball screw, a plurality of recirculating balls (16) engaged between the outer lead-screw (4) and the inner lead-screw (5) whereas the plurality of balls only engages with the cylinder piston device in the recirculation circuits (17) according to an embodiment of the disclosure;

[0040] FIG. 1 shows an illustration of the inverted ball screw device external interface (11) used for securing the device to other components, this is an illustration of one type of securing method but could be arranged in a variety of known methods, the force transmission interface to external device (7) may be arranged as threaded interface according to an embodiment of the disclosure;

[0041] FIG. 4 shows a isometrically illustration of the inverted ball screw actuator device whereas the drive side (10) is arranged as a splined interface to the power source, the drive side (10) is protruding through a sealing device (7) and connected to the outer lead-screw (4) the drive side (10) interface to power source may be arranged in a variety of known methods, according to an embodiment of the disclosure;

[0042] Exemplary embodiment of the invention FIG. 52, shows a typical layout of an inverted ball screw actuator device, comprising force transmission element interface to external device (7) inverted ball screw housing interface to external device (11), drive unit interface device (10) connected to the outer lead-screw (4) with sealing device (7) and bearings (13), piston rod (12) with sealing device (2), and bearings (13) forming one sealed off compartment, whereas the outer lead-screw is connected to the inner lead-screw through a plurality if balls where whereas the only members penetrating the said compartment is the piston rod (12) and drive unit interface, here in this illustration formed as an spline.

[0043] Further, the exemplary embodiment of the invention shown in FIG. 1, FIG. 2, FIG. 3, FIG. 4. FIG. 5, FIG. 6 and FIG. 7, illustrates the preferred embodiment of the inverted ball screw actuator device with ball screw arrangement inside a housing (3). Rotating the drive unit interface will make the outer lead-screw (2) to rotate, through the plurality of balls (16) threadingly engaged between the outer lead-screw (4), inner lead-screw (5), it will force the inner lead-screw (5) and the piston rod (12) to move laterally in and out of the housing (3) dependent on way of rotation.

[0044] FIG. 7 illustrates the preferred embodiment of the ball screw linear actuator in a so-called open view to clarify further the components included in the circulation paths of the plurality of balls in the invention.

[0045] Further FIG. 7 illustrates the preferred embodiment of the plurality of bearing balls (16), whereas the ball screw outer lead-screw (4) having outer helical ball rolling surface with ball circulation grooves configured to rotate on the inner lead-screw (5) helical ball rolling surface through the set of balls (16).

[0046] Further FIG. 7 illustrates the ball recirculation path (17) of the invention shown with a plurality of bearing balls (16) inserted in the helical path grooves. The outer lead-screw (4) rotates while the inner lead-screw is fixed to the piston rod (12) either by fasteners, by friction, by a non-circular interface or a combination of methods. The threads of the inner lead-screw (4) have a deflector system typically every 72 degree for each ball circulation circuit. Direction of rotation for the balls is given by the rotational direction of the inverted ball screw outer load-screw (2). The inverted deflector system in the inner lead-lead screws enables the balls to pass the top of the threads of the outer lead-screw (4)

[0047] FIG. 6 illustrates the inner lead-screw of the invention, the inner lead screw (5) are formed with outer bound helical grooves and deflectors spaced typically every 72 degrees for each ball circulating circuit, that when assembled with the outer lead-screw (2) forms a deflector channel that the bearing balls can advance through. The grooves of the deflector channel (17) have diameter slightly larger than the balls (16) and are formed in a way that between the deflector entrance and deflector exit the groove opening is smaller than the ball diameter such that the balls are prevented from falling out. The inner lead-screw does not rotate but are fixed to the piston rod (12). The inner lead-screw (5) is used for recirculation of the plurality of bearing balls as outlined in FIG. 7 through the bail deflector channel (17) with exit and entrance grooves. Inner and outer lead screw when invention is assembled forms a continuous groove path for the bearing balls to circulate and roll in, rolling directions of the bearing balls are determined by the direction of rotation of the ball screw nut (2).

[0048] An example of one configuration of grooves are shown in FIG. 6. As the inner lead-screw (5) is shown with deflector channels evenly spaced every 72 degree for each ball circulation circuit. The ball deflector channels are more than balls diameter deep with adequate clearance for the bearing balls to pass unimpeded over the land between the adjacent grooves of the outer lead screw (4) as shown in FIG. 4.

[0049] The illustrated embodiment in FIG. 1 to FIG. 7 preferable uses an electric motor to rotate the outer lead-screw. Electric power and communication may be supplied via a suitable electrical control lines. The control lines may be connected to a power source at suitable location either subsea or at surface. In some embodiments, the electrical control lines are coupled to control modules (not shown) and enable transfer of desired electrical signals, e.g. power and data signals (communication).

[0050] Referring now back to FIG. 1 and FIG. 3, the piston rod (12) may comprise a movable stem, or other suitable drive member which may be selectively operated via the electric motor or other type of motive member to actuate a valve or other driven component in a host at surface or subsea. According to one embodiment, the subsea electrical ball screw linear actuator comprises an actuator body having a rear face and a front face. At least one electrical connector and a mechanical interface are both positioned along the rear face.

[0051] Depending on the application, the ball screw linear actuator may be used in cooperation with various types of hosts. In subsea applications, for example, the subsea host may comprise a variety of subsea production or processing devices. Examples of such subsea host structures include a subsea tree, manifold, pump, pipeline end manifold (PLEM), pipeline end termination (PLET), or other subsea hosts.

[0052] In some embodiments, the linear ball screw actuator is used in subsea operations such as Cone Penetration Testing apparatus. Cone Penetration Test apparatus is used in the field geotechnical investigation of soil conditions. In such application the ball screw linear actuator is either connected to a umbilical for transferring power and communication or includes a battery package for operation of the linear ball screw actuator.

[0053] In some embodiments, the linear ball screw actuator is purely used to electrify hydraulic systems by replacing hydraulic cylinders both at surface, subsurface, subsea and in downhole tools

[0054] In some embodiments, the actuator mechanical interface also may comprise a bucket coupling sized and constructed for receipt in a bucket receiver of host mechanical interface. For example, the bucket coupling, and corresponding bucket receiver may be in the form of ROV bucket couplings and ROV buckets, respectively. For rotary drive members, the ROV interface between the ROV bucket coupling and bucket receiver may be constructed with a variety of cooperating configurations, e.g. according to standards described in ISO 13628-8 or API 17H.

[0055] Depending on the parameters of a given subsea operation, the electric control lines may be part of an electrical flying lead (EFL) connected between subsea control module and host electrical connectors. Additionally, actuator electrical connectors and corresponding host electrical connectors may be constructed as wet-mate connectors to facilitate coupling and decoupling in a liquid environment with simple linear motion of the electrical actuator. The installation and de-installation of the electrical actuator with respect to the host may be accomplished without a live electrical connection, i.e. without electrical power supplied to the electrical actuator during engagement and disengagement with respect to host.

[0056] The actuator mechanical interface may comprise a drive member which automatically engages the driven component, e.g. valve, via linkage or other suitable mechanism. In the illustrated embodiment, the linkage extends to and forms part of the host mechanical interface. The drive member may be in the form of a drive stem which is linearly movable by a motive member within actuator body

[0057] By way of example, if the ball screw linear actuator is used for subsea operations the electrical interface may comprise at least one electrical connector positioned along the rear face. In the example illustrated, the electrical connectors is positioned along rear face for electrical engagement with corresponding electrical connectors of host electrical interface. By way of example, the electrical connectors may comprise male/temale connectors, respectively, or vice versa.

[0058] The electrical connectors (e.g. male/female connectors) may be utilized for transmission of desired electrical signals, e.g. electrical power signals, control signals, and data communication signals.

[0059] Various types of electrical connectors and/or related components may be utilized to operate the ball screw linear actuator. One example comprises stab plate connectors. In some applications, the host electrical connectors may be installed at a fixed position on, for example, a panel of the host structure but with a predefined free-floating capability for tolerance compensation. The electrical connectors also may be constructed in the form of inductive couplings able to transmit electrical power and/or data signals