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Title:
DAMPENING SYSTEM AND METHOD
Document Type and Number:
WIPO Patent Application WO/1999/047399
Kind Code:
A1
Abstract:
A system and method for dampening rotational movement of a first rotating member (124a) according to which a second rotating member (124) operatively connected to the first rotating member for rotation therewith. At least one flyweight (136, 138) is provided which is responsive to the inertial forces caused by rotation of the second rotating member for increasing its effective length, and a plurality of friction plates (146, 148) are responsive to the increase of the effective length of the flyweight for dampening or braking the rotational movement of the second rotating member, and therefore the first rotating member.

Inventors:
Weise, Stanley Allan (221 E. Haven Road Waxahachie, TX, 75165, US)
Application Number:
PCT/US1999/005762
Publication Date:
September 23, 1999
Filing Date:
March 16, 1999
Export Citation:
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Assignee:
HALLIBURTON ENERGY SERVICES, INC. (2601 Beltline Road Carrollton, TX, 75006, US)
International Classes:
F16D55/36; F16D59/00; F16D65/14; (IPC1-7): B60T8/72
Foreign References:
US4773388A
US4809823A
Attorney, Agent or Firm:
Mccombs, David L. (Haynes and Boone, L.L.P. 3100 NationsBank Plaza 901 Main Street Dallas, TX, 75202-3789, US)
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Claims:
1. A dampening system for dampening rotation movement of a rotating member, the system comprising at least one flyweight adapted for relative pivotal movement and responsive to the inertial forces caused by rotation of the rotating member for increasing its effective length, and a dampener responsive to the increase of the effective length of the flyweights for dampening or braking the rotation movement of the rotating member.
2. The system of claim 1 wherein the dampener comprises a plurality of friction plates normally loosely stacked but adapted to frictionally engage in response to the increase in the effective length of the flyweights.
3. The system of claim 2 further comprising a housing extending over the shaft and the flyweights, a portion of the friction plates being connected to the shaft and the remaining portion of the friction plates being connected to the housing so that the friction engagement of the flyweights brakes, or dampens, the rotation of the shaft.
4. The system of claim 1 wherein there is at least one pair of flyweights, the flyweights of each pair being pivotally connected.
5. The system of claim 4 wherein the rotating member is a shaft, the flyweights being mounted relative to the shaft for rotation therewith so that they move in response to the inertial forces created during their rotation to increase their effective length.
6. The system of claim 5 wherein the flyweights pivot radially outwardly from the shaft in response to the inertial forces to increase their effective length.
7. The system of claim 6 further comprising means for urging and maintaining the flyweights in a rest position in which the effective length of each pair of flyweights is at a minimum.
8. The system of claim 4 wherein the urging means is a garter spring extending through the pivotal connection of the flyweights.
9. The system of claim 7 wherein the dampener comprises a plurality of friction plates normally loosely stacked but adapted to frictionally engage in response to the increase in the effective length of the flyweights.
10. The system of claim 9 further comprising a gear connected to the shaft so that the friction engagement of the plates dampens the rotation of the gear and any member connected to the gear.
11. The system of claim 9 further comprising a mounting plate disposed at one of the ends of the flyweights so that the increase in the effective length of the flyweights causes the mounting plate to move into engagement with one of the friction plates to establish the friction engagement between the plates.
12. The system of claim 10 further comprising a housing extending over the shaft and the flyweights, a portion of the friction plates being connected to the shaft and the remaining portion of the friction plates being connected to the housing so that the friction engagement of the flyweights brakes, or dampens, the rotation of the shaft.
13. The system of claim 4 wherein there are four pairs of flyweights angularly spaced around the shaft.
14. A method of dampening rotational movement of a rotating member, comprising the steps of pivotally mounting at least one flyweight so that it responds to the inertial forces caused by rotation of the rotating member and increases its effective length, and dampening the rotational movement of the rotating member in response to the increase of the effective length.
15. The method of claim 14 wherein the step of dampening comprises the step of rotating at least one friction plate with the shaft, fixing least one other friction plate during the rotation, and frictionally engage the plates in response to the rotation of the shaft to dampen the rotation.
16. The method of claim 14 wherein there is at least one pair of flyweights, and further comprising the step of pivotally connecting the flyweights of each pair.
17. The method of claim 16 further comprising the step of mounting the flyweights relative to the shaft for rotation therewith so that they move in response to the inertial forces created during their rotation to increase their effective length.
18. The method of claim 17 wherein the flyweights pivot radially outwardly from the shaft in response to the inertial forces to increase their effective length.
19. The method of claim 17 further comprising the step of normally urging and maintaining the flyweights in a rest position in which the effective length of each pair of flyweights is at a minimum.
20. The method of claim 14 further comprising the step of connecting a gear to the shaft so that the friction engagement of the plates dampens the rotation of the gear and any member connected to the gear.
Description:
DAMPENING SYSTEM AND METHOD Cross-reference to Related Application This application relates to provisional application S. N. 60/078,640 filed March 19,1998.

Background The present disclosure relates to a dampening system and method, and, more particularly, to such a system and method for dampening movement of a rotating member.

There are many applications that involve dampening the rotation movement of a rotating member. For example, conventional actuators employ a helically grooved ball screw that is mounted for reciprocal axial movement in a ball nut. The ball nut is secured against axial movement and is rotated to cause corresponding axial movement of the ball screw between a retracted and an extended position. Actuators are used with many devices, such as, for example, gate valves or the like, which are attached to the ball screw for translational movement therewith between a closed and open position. The ball nut can be rotated by fluid pressure as disclosed in U. S. Patent No.

4,691,893; by an electrical motor as disclosed in U. S. Patent No. 5,195,721; or in any other conventional manner.

In these arrangements a system is usually provided to dampen, or brake, the ball screw during its return, or reverse, movement back to its retracted position to prevent damage to the ball screw and its associated components and to prevent hydraulic shock to the apparatus to which the actuator is connected. Some previous designs used a hydraulic dampening system which is costly and is prone to leaking.

Other previous designs close relatively slowly, and, if the actuator is connected to a valve, or the like, excess product flow can occur after the actuator is actuated and before it actually closes the valve. Moreover, still other previous designs are too bulky, have too many parts, are not self-adjusting, do not have a variable dampening rate, and/or require frequent maintenance.

Therefore, what is needed is a dampening system for an actuator which dampens the return, or reverse, movement of the actuator, prevents damage to the ball screw and hydraulic shock and leakage, and yet closes relatively fast. Also needed is a dampening system of the above type which is relatively compact, is self-adjusting, has a variable dampening rate, and does not require frequent maintenance.

Summary Accordingly, the dampening system of the present embodiment includes at least one flyweight adapted for relative pivotal movement and responsive to the inertial forces caused by rotation of a rotating member for increasing its effective length. A dampener is provided that is responsive to the increase of the effective length of the flyweight for dampening or braking the rotation movement of the rotating member.

The dampening system of the above embodiment enjoys the advantages of being compact and mechanically operated and has relatively few parts. Also, it operates relatively quickly, but at a safe rate to prevent damage to the actuator mechanism and hydraulic shock to the pipeline/well head to which the above- mentioned valve is connected. Further, it can easily be adjusted to vary the dampening rate, requires low maintenance, is relatively compact, has relatively few parts, and is self-adjusting.

Brief Description of the Drawings Fig. 1 is a vertical sectional view of the actuator of an embodiment of the present invention shown with its ball screw in a retracted position.

Fig. 2 is an enlarged isometric view of several components of the actuator of Fig.

1, including the dampening system of the above embodiment.

Fig. 3 is an enlarged cross-sectional view of the control module of Figs. 1 and 2.

Figs. 4A and 4B are cross-sectional views of the dampening system of the above embodiment in two operational positions.

Figs. 5A-5F are plan views of various components of the dampening system of Figs. 4A and 4B.

Description of the Preferred Embodiment Referring to Figs. 1 and 2 of the drawing, the dampening system according to an embodiment of the present invention will be shown and described in connection with an actuator assembly which includes a power source, shown in general by the reference numeral 10. The power source 10 is, for the purpose of example, an AC motor which is connected in any known manner, such as by bolts, to the outer surface of one wall of a circular casing 12. An output shaft 14 extends from the motor 10 into the interior of the casing 12 where it is connected to a pinion gear 15 which is in engagement with a spur gear 16.

The spur gear 16 is circular in cross section and has a central opening which receives a shaft 18 which is coupled to the gear 16 in a conventional manner.

Therefore, rotation of the output shaft 14 by the motor 10 causes corresponding rotation of the spur gear 16 and the shaft 18. A pinion gear 20 also extends around, and is coupled to, the shaft 18 in an axially-spaced relation to the spur gear 16.

Another spur gear 22 is provided which is in engagement with the pinion gear 20.

Therefore, the above-mentioned rotation of the shaft 18 causes rotation of the pinion gear 20 to drive the spur gear 22. It is understood that the gears 15,16,20 and 22 are supported for rotation in the casing 12 in any conventional manner and that the gears are designed such that the speed of the spur gear 22 is substantially reduced from the speed of the output shaft 14 of the motor 10, in a conventional manner.

The spur gear 22 has an enlarged central opening through which a mounting flange 23 extends. An inner race 24 is threadedly connected to the mounting flange 23 and a plurality of bolts 26 extend through aligned openings in the mounting flange and the gear 22 to couple the gear to the inner race.

A portion of the inner race 24 projects upwardly, as viewed in Figs. 1 and 2, through an opening in the casing 12 and the inner and outer surfaces of the inner race 24 are stepped. A ring-shaped sprag clutch 28 extends around the mounting flange 23 and functions to permit rotation of the mounting flange, and therefore the inner race 24, in only one direction. Therefore, the above-described, relatively low-speed rotation of

the spur gear 22 causes rotation of the mounting flange 23, and therefore the inner race 24, which rotation is permitted in one, predetermined direction by the sprag clutch 28.

The upper portion of a cylindrical driver 30, as viewed in Fig. 1, extends within the upper end portion of the inner race 24. The outer surface of the driver 30 and the inner surface of the inner race 24 are stepped and complementary so that the upper portion of the inner race receives the corresponding lower surface of the driver in a slightly spaced relation. Thus, the upper portion of the inner race 24 can rotate around the overlapped lower portion of the driver 30 under conditions to be described.

A wrap spring 34 normally extends around the outer surfaces of the driver 30 and the inner race 24 in a loose fit, and functions as a clutch. To this end, a tang 34a is formed on the lower portion of the wrap spring 34 and extends into a corresponding notch formed in the outer surface of the inner race 24. A control module 40, shown generally in Figs. 1 and 2, is disposed in the upper end portion of the driver 30 and will be described in detail later. A tang 34b (Fig. 2) is formed on the upper end of the wrap spring and extends into a notch formed in a component of the control module 40. An outer race 41 extends over the mounting flange 23 and the inner race 24 and a cover 42 is mounted on the outer race and encases the control module 40, the driver 30, the wrap spring 34 and the inner race 24a.

An electrical switching device, such as a solenoid 44, is mounted to an end plate of the cover 42 and has an armature 44a that extends through an opening in the latter end plate and engages the upper portion of the control module 40. The armature 44a moves between an extended position when the solenoid is energized to actuate the control module 40 in a manner to be described, and a retracted position (under the force of a spring, or the like) when the solenoid is de-energized. The wrap spring 34, and therefore the control module 40 rotate with the inner race 24. When the armature 44a of the solenoid 44 actuates the control module 40 and the control module latches to the stationary driver 30 in a manner to be described, the upper end of the wrap spring 34 is thus restrained against movement, causing the wrap spring to tighten over

the outer surfaces of the inner race 24 and the driver 30. This couples the inner race 24 to the driver 30 and thus transmits torque from the inner race to the driver, also in a manner to be described.

It is understood that a locking device can be mounted between the control module 40 and the solenoid 44 as disclosed in co-pending application serial number (attorney's docket No. 5528.117). This locking device functions to maintain the control module 40 in an actuated condition even after the solenoid 44 has been de-energized.

The disclosure of this application is hereby incorporated by reference.

An output shaft 46 is disposed in the lower portion of the driver 30 in a coaxial relationship, extends through the inner race 24 and projects downwardly from the lower end of the inner race. A radially-extending set screw 48 extends through an opening in the driver 30 and engages the output shaft 46 to lock the shaft to the driver so that the shaft rotates with the driver.

A pinion 50 is disposed on the lower, projecting end portion of the output shaft 46 and engages a spur gear 52 which is connected to, and extends around the upper end portion of an elongated ball nut 54. The upper portion of the ball nut 54 extends in the casing 12 and the ball nut is mounted for rotation in a bearing assembly 56 located adjacent to an opening in the latter casing through which the ball nut projects.

Therefore, when the rotating inner race 24 is coupled to the driver 30 by the wrap spring 34 as controlled by the armature 44a and the control module 40 in a manner to be described, the driver 30, and therefore the output shaft 46 and the pinion 50, rotate accordingly. This rotates the gear 52 causing corresponding rotation of the ball nut 54.

A helically grooved ball screw 60 is disposed in the ball nut 54 and the inner portion of the lower end portion of the ball nut 54 is provided with a helical groove that complements the groove in the ball screw 60 so as to receive a plurality of balls 62. As a result, rotation of the ball nut 54 causes corresponding axial movement of the ball screw 60 between a retracted position shown in Fig. 1 and by the solid lines in Fig. 2, and an extended position shown by the phantom lines in Fig. 2.

A head 64 is bolted to the lower portion of the casing 12 and a housing 66 is

connected to, and extends downwardly from, the head and around the ball nut 54. A thrust bearing 68 extends in an area defined by a stepped portion of the head 64, the upper end portion of the housing 66, and a corresponding surface of the ball nut 54. A flange 54a extends radially outwardly from the lower portion of the ball nut 54 and engages the thrust bearing 68 in the retracted position of the ball screw, as shown.

The lower end portion 60a of the ball screw 60 is enlarged and is in threaded engagement with an adapter 70 that has a sleeve 70a extending in a radially-spaced relation to the ball nut 54 in the housing 66. Two elongated, diametrically opposed, slots 70b and 70c are provided in the sleeve 70a of the adapter 70 which respectively receive two radially extending set screws 74a and 74b extending through corresponding openings in the housing 66. As a result, rotation of the ball screw 60 with the ball nut 54 is prevented so that the ball screw will extend or retract axially relative to the ball nut when the nut is rotated.

The lower end of the adapter 70 abuts against a plate 75 that is connected to a spool sleeve 76 which, in turn, is connected to an upper spring plate 77. Central openings are formed through the adapter 70 and the plate 75 to permit a stem 78 to be connected to the lower end of the ball screw 60. To this end, a spring bolt 79 has a head portion 79a disposed in an enlarged opening in the lower end portion of the adapter 70 and a shaft portion 79b that extends through the opening in the plate 75 and into the upper end portion of the stem 78 and is connected to the stem in any known manner. The upper end of the stem 78 extends in a corresponding opening formed in the lower portion of the plate 75. As a result of this arrangement, the stem 78, the plate 75 and all components connected thereto, are separate from the ball screw 60 and the plate 70. This not only aids in manufacture and assembly, but insures that no torque from the rotating ball nut 54 will be applied to the stem 78 and any valve, or the like, connected thereto.

A lower spring plate 80 extends around the stem 78 and normally extends in a spaced relation to the plate 75, and a helical spring 82 extends between the upper spring plate 77 and the lower spring plate 80. The lower spring plate 80 is maintained

in a stationary position by a packing retainer 84 that extends around the stem 78 and is secured to a bonnet 86. An outer cylindrical housing 88 extends from the head 64 to the bonnet 86, is mechanically connected to both, and encloses the lower portion of the ball nut 54 and its associated components. A plurality of shims 89 are mounted on the upper surface of the spring plate 80 and control the stroke length of the ball screw 60, as will be described.

The stem 78 reciprocates with the ball screw 60 and relative to the fixed lower spring plate 80, the packing retainer 84, and the bonnet 86. The stem 78 has an enlarged lower head portion 78a which projects from the lower surface of the bonnet 86 and which is adapted to be connected to a device (not shown), such as a gate valve, which is to be actuated by the above actuator. Thus, when the ball nut 54 is rotated and the ball screw 60 moves downwardly to its extended position shown by the phantom lines in Fig. 2, it causes corresponding downward movement of the adapter 70, the plate 75, the spool sleeve 76, the upper spring plate 77 and the stem 78. The spring 82 is thus compressed between the upper spring plate 77 and the fixed lower spring plate 80 and is adapted to assist in returning the ball screw 60 back to its retracted position in a manner to be described.

Details of the control module 40 are shown in Fig. 3. More particularly, the control module 40 includes a hub 90 having a stepped outer surface that nests within the stepped inner surface of the driver 30 in a slightly spaced relationship to the driver 30 to permit rotation movement of the hub relative to the driver. Six radially- extending, angularly-spaced, passages 90a are formed through the hub 90 all of which register with a central bore 90b also extending through the hub.

Two balls 94 are disposed in each of the passages 90a and are retained therein by a retaining member 96 disposed in a groove formed in the hub 90 near the outer ends of the passages. The retaining member 96 projects slightly outwardly from the latter groove to normally retain the balls 94 in their respective passages 90a.

A plurality of holes, two of which are shown by the reference numerals 30a, are angularly spaced around the inner surface of the driver 30. Therefore, when the outer

ball 94 in each passage 90a is forced past the retaining member 96 and into a hole 30a under conditions to be described, the control module 40 is latched to the driver 30.

A plunger 100 is disposed in the bore 90b of the hub 90 and has a tapered outer surface 100a. A cup 102 is disposed in the lower portion of the hub 90, as viewed in Fig. 3, and a spring 104 extends between the lower end of the plunger 100 and the cup 102 to normally urge the plunger upwardly as viewed in Fig. 3. An annular cover disk 106 extends over the upper ends of the hub 90 and has a central opening that receives the upper end of the plunger 100 and the lower end of the armature 44a of the solenoid 44.

A pair of axially-spaced wear rings 108a and 108b are provided through corresponding grooves formed in the outer surface of the hub 90, and a washer 110 extends between two pads 112a and 112b located just above the hub 90. The outer portion of the washer 110 projects outwardly from the driver 30 and retains the wrap spring 34 adjacent to the outer surfaces of the driver 30 and the inner race 24.

(Although not clear in Fig. 2 due to limitations of scale, the tang 34b extends in a notch in the washer 110 of the control module 40.) The operation of the control module 40 will be described in detail later.

As partially shown in Fig. 2, a dampening system 120 is provided which is operatively connected to the spur gear 52, via a pinion gear 122. The system functions to dampen the rotation of the latter gear and, therefore, the gear 52 and the corresponding movement of the ball screw 60, during movement of the ball screw from its extended position to its retracted position under the force of the spring 82 (Figs. 1 and 3), and any other forces acting on the ball screw 60.

As shown in Fig. 4A, the pinion gear 122 is connected to the lower end of a splined shaft 124 in a housing 126. The shaft 124 has a reduced diameter portion 124a that extends through the bore of the gear 122 and into a bearing 125 mounted in the bottom plate 126a of the housing 126. The shaft 124 also extends through a top plate 126b of the housing 126 and projects upwardly therefrom as viewed in Fig. 4.

A housing 130 is connected to the housing 126 and encloses the projecting

portion of the shaft 124. The design is such that the shaft 124 rotates with the gear 122 when the ball screw 60 moves from its extended position to its retracted position as described above, but does not rotate with the gear 122 when the ball screw 60 moves from its retracted position to its extended position. Since this type of design is conventional, it will not be described in further detail. It is understood that the spur gear 52 is also located in the housing 126 in engagement with the pinion gear 122, but is not shown in Fig. 4A.

As shown in Figs. 4,5A, and 5B four upper centrifugal flyweight segments 136a- 136d are angularly spaced around the shaft 24. Also, four lower centrifugal flyweight segments 138a-138d are angularly spaced around the shaft 124 and extend below the upper segments, respectively, in an aligned relation thereto.

The four upper flyweight segments 136a-136d are pivotally attached to an upper mounting plate 140 having a central opening extending around the shaft 124. Similarly, the lower flyweight segments 138a-138d are pivotally attached to a lower mounting plate 142 also having a central opening extending around the shaft 124. The mounting plates 140 and 142 are attached to the shaft 124 in a conventional manner to enable them to rotate with the shaft and to slide axially relative to the shaft under conditions to be described.

As shown in Fig. 4A in connection with the flyweight segments 136a, 138a, 136c, and 138c; and in Fig. 5C in connection with the flyweight segments 136d and 138d, each upper flyweight segment 138a-138d is pivotally attached to a corresponding lower flyweight segment 138a-138d immediately below it. A garter spring 144 (Figs. 4A, 5A, and 5B) is looped through these pivot points and operates in a conventional manner to normally urge the pivot points of the segments 136a-136d and 138a-138d radially inwardly to retract the segments to their rest position shown in Fig. 4A in connection with the segments 136a, 138a, 136c, and 138c. In this position, the angular positions of the cooperating pairs of segments 136a-136d and 138a-138d are such that the effective length of each pair is at a minimum, i. e., the respective upper surfaces of the segments 136a and 136c and the lower surfaces of the segments 138a and 138c

extend in a horizontal plane as viewed in Fig. 4A in connection with the segments 136a, 138a, 136c and 138c.

As the shaft 124 rotates in response to the retraction of the ball screw 60 as discussed above, the mounting plates 140 and 142, and therefore the flyweight segments 136a-136d and 138a-138d, also rotate. This rotation generates inertial, or centrifugal, forces so that the flyweight segments 136a-136d and 138a-138d tend to move radially outwardly in the housing 130 against the force established by the garter spring 144 to the position shown in Fig. 4B in connection with the flyweight segments 136a, 138a, 136c, and 138c. Due to the design of the segments 136a-136d and 138a- 138d, and the above-described pivotal connections, this movement of the segments from their rest positions of Fig. 4A to their extended positions of Fig. 4B increases the effective axial length of each pivotally-mounted pair of upper segments. In this context, and as viewed in Fig. 4B in connection with the segments 136a, 138a, 136c, and 138c, the upper and lower surfaces of the segments extend at an angle to the above-mention horizontal plane.

Four rotating friction discs 146 and four fixed friction discs are 148 are provided with central openings and are disposed around the shaft 124 below the flyweight segments 138a-138d. The discs 146 and 148 are disposed in an alternating, loosely- stacked, relationship, with the lowest disc 148 resting on an axially fixed plate 149 also provided with a central opening extending around the shaft 124.

As better shown in Fig. 5D in connection with a disc 146, a plurality of angularly- spaced splines 146a are formed in the inner surface of each disc 146 defining the latter central opening. These splines 146a engage corresponding splines (not shown) formed on the outer surface of the shaft 124 so that the latter discs rotate with the shaft.

Similarly, as shown in Figs. 5E and 5F in connection with a disc 148, the outer circumferential edges of each disc 148 define a plurality of splines 148a which are received in grooves formed in the inner surface of the housing 130 to secure the latter discs against rotation. As a result, the discs 146 rotate with the shaft 124 and the discs 148 are fixed relative to the housing 130.

When the ball screw 60 is not moving from its extended position to its retracted position, the garter belt 144 maintains the flyweight segments 136a-136d and 138a- 138d in their rest position shown in Fig. 4A in connection with the flyweight segments 136a, 138a, 136c, and 138c. In this position, the lower surface of the lower mounting plate 142 is slightly spaced above the upper surface of the upper friction disc 146.

When the ball screw 60 moves from its extended position to its retracted position as described above, the gear 52, and therefore the gear 122, cause rotation of the shaft 124, and therefore the segments 136a-136d and 139a-138d. The segments 36a- 136d and 139a-138d thus move radially outwardly to the position shown in Fig. 4B in connection with the flyweight segments 136a, 138a, 136c, and 138c. This changes the relative angular disposition of each pair of segments 136a-136d and 138a-138d, respectively, and increases the effective axial lengths of each corresponding pair.

As a result of this effective increase in length of the segments 136a-136d and 138a-138d, the lower mounting plate 142 is forced downwardly until it contacts the upper disc 146, as viewed in Fig. 4B, and pushes down on the assembly of discs 146 and 148. The discs 146 and 148 are thus urged into a relatively high friction engagement with each other which resists the rotation of the shaft 124, and therefore the gears 122 and 52, and therefore dampens, or brakes, the latter rotation. The design is such that this resistance is generated only when the shaft is rotating in a direction corresponding to the retraction of the ball screw 60 relative to the ball nut 54, as discussed above.

An adjusting cap 150 (Figs. 4A and 4B) is in threaded engagement with the upper end portion of the housing 130, and a bearing mount 152 extends between the cap and the upper bearing plate 140 and around a bearing 154 to permit rotation of the shaft 124 relative to the mount 152. Thus, rotation of the cap 150 so that it moves axially relative to the housing 130 varies the axial position of the bearing plate 140 and therefore the starting angle between the segments 136a-136d and the segments 138a- 138d, respectively and thus also varies the force amplification.

In operation of the actuator assembly, it will be assumed that the assembly is

oriented as shown in Figs. 1 and 2, i. e., so that the ball screw 60 moves downwardly towards its extended position, and upwardly to its retracted position. It will also be assumed that the armature 44a of the solenoid is in its de-energized, retracted position of Fig. 3; the ball screw 60 is initially in its fully retracted position, and the friction plates 146 and 148 are in a loosely stacked position.

The solenoid 44 is initially actuated causing its armature 44a to push the plunger 100 of the control module 40 downwardly against the force of the spring 104. During this downward movement of the plunger 100, the tapered surface 100a of the plunger engages the inner ball 94 in each passage 90a and forces the balls 94 radially outwardly, causing the outer ball in each passage 90a to be forced past the retaining member 96 and into a corresponding hole 30a of the driver 30. This latches the control module 40 to the driver 30 and permits the wrap spring 34 to couple the inner race 24 to the driver 30 as will be described.

The motor 10 is then turned on which drives its output shaft 14, the gear 16, and therefore the shaft 18, and the pinion 20. The pinion 20, in turn, drives the gear 22 and therefore the inner race 24, with the above-described gears and pinions reducing the rotation speed of the inner race when compared to that of the output shaft 14 of the motor 10. Since the tangs 34a and 34b of the wrap spring 34 are respectively connected to the inner race 24 and to the control module 40, this rotation of the inner race 24 causes rotation of the wrap spring 34 and therefore the control module 40.

Since the balls 94 of the control module 40 are extending in the holes 30a of the driver 30, this initial rotation of the control module 40 causes the wrap spring 34 to immediately tighten over the driver 30 and couples the inner race 24 to the driver in the manner described above. Therefore, the driver 30 and the shaft 46 also rotate at the same reduced speed.

The rotation of the shaft 46 causes corresponding rotation of the pinion 50, the gear 52, and the ball nut 54, causing the ball screw 60 to move axially from its retracted position to its extended, operative position. The plate 75 and the stem 78 also move with the ball screw 60 to its extended position until the plate 75 (Fig. 1) engages the

shims 89 on the fixed lower spring plate 80, and the spring 82 is compressed accordingly. If a gate valve, or other device, is connected to the stem 78, the gate valve would be in its actuated position, which could be either opened or closed, depending on the particular design of the system.

As discussed above, during the above movement of the ball screw 60 from its retracted position to its extended position, the gear 122 rotates with the gear 52 but the shaft 124, and therefore the segments 136a-136d and138a-138d, do not rotate. Thus, the segments 136a-136d and 138a-138d are maintained in their rest position shown in Fig. 4A by the garter spring 144. In this rest position, the effecting lengths of the pairs of segments 136a-136d and 139a-138d are at a minimum and the friction discs 146 and 148 thus stay in their loosely stacked position and therefore do not impede this movement of the ball screw 60.

In the fully extended, operative, position of the ball screw 60, the motor 10 is turned off by a position sensor, a timer, or the like. The ball screw 60 is maintained in the latter position by the extended armature 44a of the solenoid 44 maintaining the plunger of control module 40 in its lower position which, in turn, maintains the connection between the inner race 24 and the driver 30. The sprag clutch 28 prevents back rotation of inner race 24, and therefore the gears 22,20,16 and 15, under the force of the compressed spring 82 and any other external forces acting on the ball screw 60.

In the event it is desired to move the ball screw 60 and the stem 78 back to their retracted positions, or in the event of a power failure, the solenoid 44 is de-energized.

This causes the armature 44a to retract and, as a result, the plunger 100 of the control module 40 is thus urged upwardly by the spring 104 to its upper position shown in Fig.

3. This permits the balls 94 of the control module 40 to disengage from the holes 30a in the driver 30 and unlatch the control module from the driver. As a result, the wrap spring 34 is loosened and thus releases the coupling between the inner race 24 and the driver 30. The forces exerted by the compressed spring 82 on the upper spring plate 77, and therefore the plate 75, as well as any external forces, such as valve body

pressure, or the like, acting on the stem 78, forces the ball screw 60 upwardly towards its retracted position.

Since the driver 30 is decoupled from the inner race 24, this upward movement of the ball nut 54 causes rotation of the gear 52, the pinion 50, the output shaft 46 and the driver 30 in a direction that is opposite to the direction of rotation discussed above in connection with the extension of the ball screw 60. This rotation of the gear 52 also causes corresponding rotation of the gear 122 which is coupled to the shaft 124 when rotating in this opposite direction. The rotation of the shaft 124 causes corresponding rotation of the segments 136a-136d and 139a-138d which creates inertial, or centrifugal forces, causing the segments to move radially outwardly to the position shown in Fig. 4B in connection with the flyweight segments 136a, 138a, 136c, and 138c. This changes the relative angular disposition of the segments 136a-136d and 138a-138d, and thus increases the effective axial lengths of each corresponding pair of segments, as discussed above.

As a result, the lower mounting plate 142 is forced downwardly until it contacts the upper disc 146 and pushes down on the assembly of discs 146 and 148 to urge them into a relatively high friction engagement. This friction between the discs 146 and 148 resists the rotation of the shaft 124, and therefore the gears 122 and 52 and therefore dampens, or brakes, the latter rotation, which, in turn dampens, or brakes the retraction of the ball screw 60.

This retracting movement of the ball screw 60 continues until the ball screw reaches the fully retracted position, with the sprag clutch 28 preventing back rotation of the remaining gear train, as discussed above. Thus, the stem 78, as well as any device connected to the stem, would also be moved back to its original position.

As discussed above, a locking device (not shown) can be mounted between the solenoid 44 and the control module 40 for the purpose of locking and maintaining the ball screw 60 in its fully extended position or in any position between its fully retracted and fully extended position, even if the solenoid 44 is de-energized.

The dampening system and the actuator assembly of the above embodiment

thus enjoy several advantages. For example, it is compact and mechanicaily operated and has relatively few parts. Also, it operates relatively quickly, but at a safe rate to prevent damage to the actuator mechanism and hydraulic shock to the pipeline/well head to which the above-mentioned valve is connected. Further, it can easily be adjusted to vary the dampening rate, and requires low maintenance.

It is understood that other components, such as a mechanical override, and a torque limiter can be provided with the assembly of the present above actuator, but have not been shown or described in detail for the convenience of presentation.

It is also understood that variations may be made in the foregoing without departing from the scope of the present invention. For example, the number of flyweight segments and friction plates can vary within the scope of the invention. Also, dampening system disclosed above is not limited to use with the actuator assembly disclosed above, or with any actuator assembly. Also, the spatial references, such as "upper","lower","downwardly","horizontal", and the like, are for the purpose of example only and are not intended to limit the specific location and orientation of the components described above.

Other modifications, changes and substitutions are intended in the foregoing disclosure and in some instances some features of the invention will be employed without a corresponding use of other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.