US3288962A

US3288962A - Valve-actuating device

Info

Publication number: US3288962A
Application number: US383112A
Authority: US
Inventors: Fry Jeremy Joseph
Original assignee: Rotork Engineering Co Ltd
Current assignee: Rotork PLC
Priority date: 1964-07-16
Filing date: 1964-07-16
Publication date: 1966-11-29
Anticipated expiration: 1983-11-29

Description

NOV. 29,. 1966 J, J F

VALVE-AGTUATING DEVICE 3 Sheets-Sheet 1 Filed July 16, 1964 m m .I E W, ..H 3 M aw m IW/ 1966 J. J. FRY 3,288,962

VALVE-ACTUATING DEVICE Filed July 16, 1964 5 Sheets-Sheet 2 INYENTUR. y

Nov. 29, 1966 J. J. FRY 3,288,962

VALVE-ACTUATING DEVICE Filed July 16, 1964 5 Sheets-Sheet 5 INVENTU/I. Jere yx/oseo/l 11y fl w/M 21L 7 224244 VWM/AM/ I ATTURNEfi United States Patent 3,288,962 VALVE-ACTUATING DEVICE Jeremy Joseph Fry, Somerset, England, assignor to Rotork Engineering Company Limited, Somerset, England Filed July 16, 1964, Ser. No. 383,112 7 Claims. (Cl. 200-6139) This invention relates to actuators more particularly, but not exclusively, for the operation of valves.

The invention is generally concerned with actuators of the kind which are power and/or manually operable whereby the output shaft or valve spindle may be selectively operated either by the power means, for example an electric motor, or by the manual means. The power means is drivably connected with the output shaft or valve spindle through a connection which generally comprises a worm on the main drive shaft and which meshes with a worm wheel on the output shaft or valve spindle.

US. Patent 3,198,033 has described an actuator con struction of the kind set out above. The power means comprises an electric motor the output shaft of which comprises the main drive shaft of the actuator on which the worm is mounted. In this actuator construction the main drive shaft is mounted for axial movement in response to resistance to movement due to an increase in torque, for example as the valve reaches its closed position. The axial movement of the main drive shaft is obtained by resilient means such as one or more packs of Belleville washers which are mounted at one or both ends of the main drive shaft so as to permit the axial movement as the torque or resistance to movement occurs as the valve reaches its closed position. This axial movement of the main drive shaft is utilized to operate torque switches which deenergize the motor circuit.

The arrangement described above operates satisfactorily if the drive connection between the main drive shaft and the output shaft of the valve spindle is irreversible. In many cases, however, the required ratio will provide a reversible worm and wheel which will permit the resilient means, i.e. the pack or packs of Belleville washers, to return the main drive shaft axially to its normal or central position when the motor is de-ener gized. In such an arrangement the return movement of the main drive shaft resets the torque switch so that the motor will be reenergized when the main operating button is depressed. Under many conditions it has been discovered that the operator frequenty maintains the starter button depressed during the operation of the actuator so that whenthe torque switch is tripped the deenergization of the motor permits the torque switch to reset itself and again energize the motor, thus producing a hammer effect due to the continued energization and deenergization of the motor.

It is, therefore, the object of the invention to provide an improved arrangement which prevents the resetting of the torque switch once the switch has been tripped due to the axial movement of the main drive shaft. A further object of the invention is to provide a torque switch latching device which retains the torque switch in its tripped position until the output shaft or valve spindle moves a predetermined amount in the opposite direction. The arrangement is particularly useful in cases where the torque switch has been operated as a result of an increase in torque due to a stuck vavle as the actuator must be moved in the opposite direction before it can be again operated in the original direction of movement.

In its broadest aspect the invention provides an actuator, more particularly for operating valves or like members, said actuator comprising a main drive shaft which is drivably connected with an output shaft or spindle through a worm mounted on the drive shaft and meshing Patented Nov. 29, 1966 with a worm wheel mounted on the output shaft or valve spindle, said main drive shaft being movable axially to operate a torque switch so as to deenergize the circuit of a motor or like power means driving said main drive shaft, wherein the torque switch is provided with latching means which maintains the torque switch in its inoperative or tripped position until the output shaft or valve spindle of the actuator is moved in the opposite direction.

In the preferred embodiment of the invention the main drive shaft of the actuator is axially movable in one or other direction and this movement is adapted to rotate a lever mechanism in a corresponding direction to operate one of a pair of torque switches. The torque switches are conveniently operated by a pivoted switch member which is movable by the lever mechanism, said latching means being pivotally mounted on said switch member whereby the movement of the switch member to operate one of said torque switches moves said latching means into position against a rotatable shaft geared to the output shaft or valve spindle of the actuator so as to maintain the switch member in the torque switch tripped position. The latching means preferably comprises a pair of pivotally mounted pawls which are urged each to engage said rotatable shaft by resilient means upon rotation of switch member in a corresponding direction. The ends of the pawls engage a knurled portion of said rotatable shaft so that the pawls are positively moved outwardly from their engaged position upon rotation of the shaft to allow the switch member to return to its normal inoperative position.

The invention will now be described by way of example with reference to the accompanying drawings, in which:

FIGURE 1 is a sectional side elevation of a portion of a control unit for a valve actuator and which embodies the features of the present invention;

FIGURE 2 is a view taken on the line 22 of FIG- URE l with the spring removed;

FIGURE 3 is an end view of the mechanism as shown in FIGURE 1 as viewed from the left-hand side of FIG- URE 1; and

FIGURE 4 is a view similar to FIGURE 3 but showing one of the torque switches tripped by the switch member which is held in its switch operated position by one of the latching pawls.

Referring now to the drawings there is shown a control unit 10 which preferably forms part of an actuator of the kind described in our copending Patent No. 3,198,033 to which reference should be made for details of the actuator construction and operation.

As described in the copending Patent No. 3,198,033 the valve actuator is intended for both power and manual operation. The power means comprises an electric motor and the main drive shaft is drivably connected with the output shaft or valve spindle of the actuator through a coupling device which comprises a worm and worm wheel. The worm is mounted on the main drive shaft and meshes with the worm wheel on the output shaft and the arrangement is such that the main drive shaft is axially movable in response to resistance to movement of the output shaft which occurs, for example, when the valve reaches its closed position. The axial movement is obtained by providing resilient means which may comprise one or more packs of Belleville washers mounted at one or both ends of the main drive shaft.

The axial movement of the main drive shaft in one or other direction is utilized to operate one or other of a pair of torque switches to deenergize the motor circuit. The torque switches are mounted in the control unit 10 and are shown by the

references

11 and 12. The control unit 10 comprises a front plate 13 and a back plate 14 which are connected by bolts to the wall 16 of the ac- "tuator casing. The end of the main drive shaft of the actuator is shown by the reference 17 and the axial movement of this shaft is converted into a corresponding rotary movement of a shaft 18 mounted in the control unit by means of a mechanism shown generally by the reference 19 and which is shown in FIGURES 1 and 2 of the drawings.

As shown particularly in FIGURE 2 of the drawings the mechanism 19 comprises a sleeve 20 which is attached to the shaft 18 by a pin 21 so as to be rotatable therewith. One end of the sleeve 20 abuts the back plate 14 of the control unit 10 while the other end of the sleeve 20 is formed with a flange 22 which surrounds the end 17 of the main drive shaft. The sleeve 20 is formed with a pair of oppositely located slots 23 which extend helically around the sleeve and which are adapted to receive a cross pin 24 as shown in FIGURE 1 of the drawings. In the drawings the cross pin 24 is shown abutting the flange 22 and the cross pin 24 is urged to this position by a spring 25 which abuts the cross pin 24 at one end and the back plate 14 at its other end. The cross pin 24 is restrained against rotational movement by the engagement of its ends in axial slots 26 which are formed in the partition wall 16 of the actuator casing. As shown in FIGURE 1 of the drawings the end of the drive shaft 17 abuts the cross pin 24 and the arrangement is such that an axial movement of the drive shaft 17 to the left as shown in FIGURE 1 of the drawings will force the cross pin 24 in a similar direction so that its ends will move along the slots 26 in the partition wall 16. At the same time the cross pin 24 will be forced along the pair of oppositely positioned slots 23 in the sleeve and due to the helical nature of the slots the movement of the cross pin 24 will force the sleeve 20 to rotate. The rotational movement of the sleeve 20 is transmitted to the shaft 18 and this movement is clockwise as viewed in FIGURE 3 of the drawings.

In FIGURE 3 of the drawings the shaft 18 is shown in its inoperative or central position and in this position of the shaft 18 the cross pin 24 will be located at an inter- .mediate position along the slots 23, so that an axial movement of the drive shaft 17 to the right as seen in FIG- URE 1 will permit the spring 25 to urge the cross pin 24 to follow the shaft 17, which in this direction of movement will result in an anticlockwise rotation of the shaft 18 from its central position as seen in FIGURE-3 of the drawings.

The

torque switches

11 and 12 are operated by a switch member 27 which is pivotally mounted on the shaft 18 and is freely rotatable relatively thereto. The switch member has a projection 28 extending through a slot 29 in the front plate 13 of the control unit and the projection 28 is engaged in one or other direction by a lever mechanism shown generally by the reference numeral 30 and which is actuated by the rotation of the shaft 18.

The lever mechanism 30 includes a rod 31 which is fixedly secured, as by brazing, to a collar 32 which is mounted on the shaft 18 and secured to it by means of the set screw 33. A flat plate 34 is freely mounted on the shaft 18 between the collar 32 and the front plate 13. The plate 34 is pivotally movable in response to angular movement of the rod 31 and as shown more particularly in FIGURES 3 and 4 of the drawings it will be seen that the plate is provided with a projecting pin 35 which abuts one side of the rod 31. In the position of the lever mechanism as shown in FIGURE 3 of the drawings a counterclockwise movement of the rod 31 in response to an axial movement of the shaft 17 to the right as seen in FIGURE 1 of the drawings, will cause the rod to abut the pin 35 and so move the plate 34 counterclockwise as viewed in FIGURE 3. The plate 34 is also provided with two tadjustable cam members 36 and37 which are angularly positioned as desired by adjusting screws 38 mounted on the front of the plate 34. As shown in FIGURES 3 and 4 of the drawings the

cam members

36 and 37 have a curved configuration and as the plate 34 rotates in a counterclockwise direction the cam member 37 is adapted to engage the projection 28 on the switch member 27 so as to actuate the torque switch 11. It will be appreciated that ad justment of the screw 38 will vary the engagement of the cam member 37 with the projection 28 so that the operation of the torque switch 11 can be altered to suit the rotational movement of the shaft 18 when the unit has been assembled.

The operation of the switch member 27 in response to an axial movement of the main drive shaft 17 to the right as viewed in FIGURE 1 is a positive movement obtained by a direct mechanical engagement of the rod 31 with the pin 35 on the plate 34. Such a positive mechanical movement is permissible as the shaft 18 rotates in response to an axial travel of the sleeve 20 to the right solely under the influence of the spring 25 and this move ment only continues until the torque switch 11 is tripped. However, in the opposite direction of travel of the shaft 17 a positive force is applied to the left on the sleeve 20 which thereby rotates the shaft 18 until the motor is deenergized. This movement could result in damage to the operating parts, in particular the lever mechanism 30, and consequently in this direction of movement a safety device must be included so as to avoid any possibility of damage to the mechanism. Axial movement of the motor shaft 17 to the left as seen in FIGURE 1 of the drawings produces a clockwise movement of the rod 31 as seen in FIGURES 3 and 4. This movement of the rod 31 is transmitted to the plate 34 by means of a coiled compression spring 39 which is attached at one end to a lug 40 formed upon the plate 34 and at the other end to a bent over portion 41 of the rod 31. As before the clockwise rotation of the plate 34 will engage the adjustable cam member 36 against the projection 28 on the switch member 27 which is thereby pivoted about the shaft 18 to trip the torque switch 12. When the torque switch 12 has been tripped any further angular movement of the rod 31 in response to rotation of the shaft 18 will be taken up by the spring 39 so that no additional positive force will be applied to the plate 34 and the switch member 27.

As previously mentioned the present invention is intended to provide a latching device whereby the switch member 27 will be maintained in its tripped or switch operated position irrespective of a subsequent return movement of the shaft 18 which may occur, for example, with an actuator in which the drive connection between the main motor shaft and the output shaft is reversible.

The latching device is shown generally by the reference numeral 43 and it comprises a pair of pivoted

pawls

44 and 45 in the form of bell crank levers and which are pivotally mounted at 46 and 47 respectively on a lower extension 48 of the switch member 27. The inoperative position of the latching device 43 is shown in FIGURE 3 of the drawings and it will be seen that the

upper arms

49 and 50 of the

pawls

44 and 45 are connected together by a coiled compression spring 51. The ends of the

pawls

44 and 45 abut the top of a rotatable shaft 52 and the arrangement is such that the pawl 44 is constantly urged in a clockwise direction as viewed in FIGURE 3, while the pawl 45 is constantly urged in a counterclockwise direction.

Referring now to FIGURE 4 of the drawings it will be i seen that the torque switch 12 has been actuated by reason of :a clockwise movement of the rod 31 which has thereby rotated the plate 34 by reason of the resilient con nection through the spring 39. The resulting rotational movement of the switch member 27 has caused the lower part 48 of the switch member of similarly move in a clockwise direction about the shaft 18. In the tripped position of the torque switch 12 as shown, the pawl 44 has moved outwardly across the top of the shaft 52 so that the end of the pawl now abuts the shaft 52 under the influence of the spring 51 whereby the longitudinal axis of the pawl 44 extends substantially radially with re spect to the shaft 52. The rotational movement of the pawl 44 is restricted by means of the stop pin 53 and a similar pin is provided to restrict the rotational movement of the pawl 44 when thelatch member 48 is moved in the opposite direction due to actuation of the torque switch 11 by the switch member 27.

The position as shown in FIGURE 4 of the drawings maintains the pawl 44 engaged with the shaft 52 which thereby prevents the return counterclockwise movement of the switch member 27 even though the rod 31 may have returned to its central or inoperative position as shown in FIGURE 3 of the drawings. The latching device 43 can only be released by rotation of the shaft 52 in a clockwise direction as viewed in FIGURES 3 and 4 of the drawings. To this end the shaft 52 is provided with a knurled section 54 which is engageable by the ends of the

pawls

44 and 45.

In the embodiment of the invention as shown in the drawings the shaft 52 is rotated in response to movement of the output shaft of the actuator and the arrangement'is such that the actuator must be operated in the opposite direction whereby the direction of rotation of the shaft 52 is such as to release the latching device 43. Conveniently the shaft 52 forms part of the limit switch actuating mechanism which may be of the kind described in our copending Patent No. 3,198,033 to which reference should be made for the details of the switch actuating mechanism. Briefly, however, the shaft 52 is drivably coupled at its right-hand end as shown in FIGURE I of the drawings with the output shaft of the actuator, for example through a worm and worm wheel drive connection. The shaft 52 extends through the wall 16 of the actuator casing and it is provided with a hollow threaded spindle 55 which frictionally engages the shaft 52 for rotation therewith under normal operating conditions. The right-hand end of the spindle 55 is provided with a stop member 56 which frictionally seats within a fixed member 57 secured to the shaft 52. The other end of the spindle 55 is provided with a stop member 58 which is secured in position on the spindle 55 by the lock nut 59. A nut member 60 is suitably mounted on the spindle 55 and is restrained against angular movement by means of a pin (not shown) which engages a notch in the nut member and which is positioned by resilient means 61. The arrangement is such that the nut member travels axially along the threaded spindle 55 in one or other direction depending upon rotation of the shaft 52. At the end of its axial travel in one or other direction the nut member 60 engages the stop member 58 or the stop member 56 and subsequent rotation of the spindle 55 by the shaft 52 produces an angular movement of the nut member 60. This angular movement of the nut member 60 is adapted to move a plate 62 angularly about the shaft 18. As shown the plate 62 engages a notch 63 in the nut member 60 and the plate is freely supported by the collars 64, 65 on the shaft 18. A limit switch actuating plate 66 is also freely mounted on the shaft 18 and the plate 66 has a foot portion 67 which projects within a cut-away portion 68 in the plate 62. The foot portion 67 is provided with a thickened portion 69 which is positioned closely adjacent a similarly thickened portion 70 in the plate 62. A spring device 71 is mounted on the shaft 18 between the collar 64 and the plate 66 and the spring has its end portions downwardly extending from the shaft 18, one end portion 72 as shown in FIGURE. 1 of the drawings, being positioned to extend downwardly at one side of the thickened

portions

69 and 70 of the plates 66 and 62 respectively. The other end portion of the spring 71 similarly extends downwardly and is positioned on the other side of the thickened

portions

67 and 70. The spring 71 thereby acts as a transmission device between the plate 62 and the switch operating plate 66. Under normal operating conditions the angular movement of the plate 62 is directly transmitted to the switch operating plate 66 through the spring 71. In the event of continued angular movement of the plate 62 after the limit switch or switches have been tripped by the plate 66, this further movement will be taken up on one or other of the ends of the spring 71 which will follow the further angular movement of the plate 62 without affecting the plate 66.

The limit switch mechanism is completed by means of a rod which extends axially parallel to the hollow spindle 55 and is provided with hooked ends 75 located on the shaft 52. The parallel rod section which is not shown engages a notch in the nut member 63 so that the rod is movable angularly when the nut member 60 reaches its limit positions. This angular movement of the rod is utilized to operate an end position indicator in accordance with conventional practice. The mechanism is completed by a lock nut 76 and a compression spring 77.

Referring now to FIGURE 4 of the drawings the latching device 43 is shown in its operative position in which the switch member 27 is maintained in its switch actuated position in which the torque switch 12 is tripped. The operation of the torque switch 12 deenergizes the motor of the actuator and in certain circumstances this results in a movement of the shaft 17 to its central or normal position. As a result the shaft 18 rotates to return the rod 31 to its central or inoperative position as shown in FIGURE 3 of the drawings. The plate member 34 moves counterclockwise with the rod 31 which in this direction of movement engages the pin 35, but the switch member 27 is unable to release the torque switch 12 due to the engagement of the end of the pawl 44 on the shaft 52. Any further attempt by the operator to reenergize the actuator in the same direction of movement will thereby have no effect due to the deenergization of the corresponding motor circuit by reason of the tripping of the torque switch 12. The invention is such that the torque switch 12 can only be released by energizing the actuator motor in the opposite direction and the subsequent movement of the actuator rotates the shaft 52 in a clockwise direction as viewed in FIGURE 4 which thereby moves the pawl 44 counterclockwise by reason of the knurled surface 54 and as the pawl 44 is released the spring 51 returns the pawl to its inoperative position as shown in FIGURE 3 of the drawings. The operator can now subsequently reenergize the actuator motor in the original direction of rotation and the arrangement is particularly useful especially when the operation of the torque switch was due to a stuck valve.

It will also be appreciated that the invention provides a simple arrangement which prevents the continued energization and deenergization of the electric motor of the actuator if the operator keeps the main starter button depressed when the actuator is moving in its valve closed direction. The invention therefore avoids the repeated hammer movement which always occurs due to the continued reenergization of the motor and is therefore of considerable value in preventing unnecessary damage to the actuator parts.

The electrical control unit as shown in FIGURE 1 of the drawings includes torque switches 11 and 12 which are operable by the switch member 27 in response to axial movement of the main drive shaft, together with limit switches (not shown) which are operable by the switch plate 66 in response to output movement of the actuator. If desired the

switches

11 and 12 may also operate as limit switches and in such an arrangement the stops 80 are fitted in the plate 48 for engagement by the plate 62.

I claim:

1. An actuator for operating valves and the like comprising a main drive shaft which is drivably connected with an output shaft through a worm mounted on the drive shaft and meshing with a worm wheel mounted on the output shaft, said main drive shaft being movable axially to operate a torque switch to deenergize the circuit of a motor driving said main drive shaft, wherein the torque switch is provided with latching means which 7 maintain the torque switch in its inoperative position until the output shaft is moved at least one full rotation in the opposite direction.

2. An actuator as claimed in claim 1 wherein said main drive shaft is axially movable and is adapted to rotate a lever mechanism in a corresponding direction to operate one of a pair of torque switches.

3. An actuator for operating valves and the like comprising a main drive shaft drivably connected with an output shaft through a worm mounted on the drive shaft and meshing with a worm wheel mounted on the output shaft, said main drive shaft being axially movable to rotate a lever mechanism in a corresponding direction to operate one of a pair of torque switches to deenergize the power circuit of .a motor driving said main drive shaft, said torque switches being operated by a pivoted switch member movable by said lever mechanism, latching means pivotally mounted on said switch member whereby the movement of the switch member to operate one of said torque switches moves said latching means to position against a rotatable shaft geared to the output shaft of the actuator to maintain the switch member in the torque switch tripped position until the output shaft is moved in the opposite direction.

4. An actuator as claimed in claim 3 wherein the latching means comprises a pair of pivotally mounted pawls each of which are resiliently urged to engage said rotatable shaft upon rotation of said switch member in a corresponding direction.

5. An actuator as claimed in claim 4 wherein the ends 8 of the pawls engage a knurled portion of said rotatable shaft.

-6. An actuator as claimed in claim 3 wherein the rotatable shaft forms a part of a limit switch actuating mechanism operable in response to the output movement of the output shaft of the actuator.

7. An actuator for operating valves comprising a main drive shaft, a worm mounted on said drive shaft, an output shaft, a worm wheel mounted on said output shaft in meshing engagement with said worm, said main drive shaft being movable axially to operate one of a pair of torque switches to deenergize the circuit of a motor drivin-g said main drive shaft, the main drive shaft rotating a lever mechanism in a cor-responding direction to operate one of said pair of torque switche by a pivoted switch member movable by said lever mechanism, latching means being pivotally mounted on said switch member whereby the movement of the switch member to operate one of said torque switches moves said latching means into position against a rotatable shaft geared to the output shaft of the actuator to maintain the switch member in the torque switch tripped position until the output shaft of the actuator is moved in the opposite direction.

References Cited by the Examiner UNITED STATES PATENTS 2,994,756 10/1961 Gessell 200'6l.39 X 3,192,335 6/1965 Todd et al 20061.39 X

BERNARD A. GILHEANY, Primary Examiner. J. BAKER, Assistant Examiner.

Claims

1. AN ACTUATOR FOR OPERATING VALVES AND THE LIKE COMPRISING A MAIN DRIVE SHAFT WHICH IS DRIVABLY CONNECTED WITH AN OUTPUT SHAFT THROUGH A WORM MOUNTED ON THE DRIVE SHAFT AND MESHING WITH A WORM WHEEL MOUNTED ON THE OUTPUT SHAFT, SAID MAIN DRIVE SHAFT BEING MOVABLE AXIALLY TO OPERATE A TORQUE SWITCH TO DEENERGIZE THE CIRCUIT OF A MOTOR DRIVING SAID MAIN DRIVE SHAFT, WHEREIN THE TORQUE SWITCH IS PROVIDED WITH LATCHING MEANS WHICH MAINTAIN THE TORQUE SWITCH IN ITS INOPERATIVE POSITION UNTIL THE OUTPUT SHAFT IS MOVED AT LEAST ONE FULL ROTATION IN THE OPPOSITE DIRECTION.