Drive mechanisms, more particularly for valve actuators

This invention relates to a motorized actuator in which the motor shaft is drivably connected with the output shaft through an intermediate shaft assembly. The motor shaft assembly includes a worm and wormwheel which is formed with cut-outs each drivably receiving the extended ends of some of the teeth of a pinion which forms part of the intermediate shaft assembly. The pinion is at all times in driving engagement with a gear on the output shaft and is axially movable by a lever to disengage the motor drive so as to allow independent manual operation of the pinion and thereby the output shaft by a handwheel mounted on a shaft. The shaft is drivably coupled with a wormwheel which is in driving engagement with the pinion by means of the driving lugs.

This invention relates to drive mechanisms, such as valve actuating 
mechanisms, for transmitting a controlled drive from a driving member to a 
driven member. In particular, but not exclusively, the invention relates 
to mechanisms by which a drive is transmitted from the power unit of a 
motorised actuator to its output shaft for operating, for example, a 
valve. 
In motorised actuators as presently manufactured, such as those described 
in our British Pat. Nos. 939,353 and 998,596, the power unit comprises an 
electric motor driving a worm and wheel, the wormwheel of which is 
positively connected to the output shaft of the actuator through a keyed 
driving member or clutch ring. The drive mechanism of such an actuator is 
thereby controlled by the de-energisation of the motor which is achieved 
by the actuation of torque and/or limit switches directly operable either 
by the axial movement of the wormshaft due to torque output (load) or the 
rotation of the output shaft (centre column of the actuator) indicating an 
output position of the actuator. 
Actuators of the kind described above operate satisfactorily, but present 
conventional arrangements have some disadvantages one of which is the 
problems involved in the operation and maintenance of the clutching 
mechanism due to its location on a shaft taking a high torque. 
The present invention sets out to overcome this disadvantage by providing a 
drive arrangement incorporating an intermediate shaft assembly, the motor 
being drivably connected with the intermediate shaft assembly by a 
conventional worm and wheel, and the intermediate shaft assembly being 
drivably connected with the main output shaft by a final drive consisting 
for example, of a spur gear or helical gear and pinion. 
The drive arrangement of the invention enables the hand/auto clutching 
mechanism to be located as part of the intermediate shaft assembly and the 
invention is particularly concerned with the construction and operation of 
the clutching mechanism of the intermediate shaft assembly. 
The provision of the intermediate shaft assembly in the drive mechanism of 
the invention also enables a more efficient and compact drive arrangement 
to be provided in that the worm/wormwheel ratio may be reduced. The 
arrangement also gives more flexibility in that a range of speeds can be 
obtained when limited to only two or three motor input speeds.

Referring now to the drawings and in particular to FIG. 1, the actuator of 
the invention comprises a main casing 10 which is normally positioned 
substantially vertically and to which is attached a horizontally located 
casing 11 which communicates with main casing 10 and houses a reversible 
electric motor 12. The motor 12 comprises a fixed stator 13 and a rotor 14 
which is attached to the driving shaft 15 of the motor. One end of shaft 
15 extends into casing 10 and is supported by main needle bearing 16. The 
other end of the shaft 15 in casing 11 is supported by a ball bearing 17 
and axial movement of the motor shaft 15 in its bearings is permitted by a 
spring arrangement which comprises a pack of Belleville washers 18A and 
18B located one on each side of bearing 17 and engaging at their outer 
ends shoulders or other projections 19A and 19B carried by the shaft. The 
arrangement ensures the return of the shaft 15 to its normal or central 
position following axial movement in one or other direction as will be 
hereinafter described. 
The motor casing 11 is completed by cover 20 which retains bearing 17 in 
position. 
A worm 21 is rigidly coupled to the motor shaft 15 in the main casing 10 
and the worm is at all times in driving engagement with a wormwheel 22 
which is mounted as will be hereinafter described on an intermediate shaft 
assembly which is indicated generally in FIG. 1 by reference 23 and which 
is located in a short housing 24. 
The intermediate shaft assembly 23 includes a manually operable clutching 
mechanism whereby wormwheel 22 may be drivably connected with a spur gear 
25 fixedly attached to a hollow output shaft 26 also vertically located in 
housing 24. The output shaft 26 is retained in housing 24 by the location 
of gear 25 between the main journal end faces. The output shaft 26 has end 
oil seals 27 which are retained axially in housing 24 by plates 28. The 
shaft 26 has a keyed extension 29 for connection to a member such as a 
valve spindle (not shown). 
The actuator as described above is normally operated by motor 12 to rotate 
the output shaft 26 in one or other direction and as previously mentioned 
the drive mechanism may be controlled by de-energisation of the motor in 
response to torque output and/or the output position of the actuator. In 
this connection torque control is achieved by the axial movement of the 
motor shaft 15 in response to a predetermined torque due e.g. to 
resistance to movement of the valve and this axial movement is utilized to 
operate torque switches in the motor circuit by means of the torque 
responsive arm 30 (FIG. 1). The position control of the actuator is 
determined by the rotation of the output shaft 26 and as shown in FIG. 1 
the spur gear 25 is in driving engagement with a pinion 31 on a shaft 32 
having a wormgear 33 meshing with wormwheel 34 on a limit shaft 35. The 
rotation of limit shaft 35 is utilized in conventional manner to trip 
limit switches in the motor circuit. 
The intermediate shaft assembly 23 provides a driving connection between 
the wormwheel 22 and gear 25 on the output shaft 26 by means of a pinion 
member 36 which forms part of a manually operable clutch drive which 
enables the output shaft 26 to be drivably disconnected from the motor 12 
for operation manually e.g. by a handwheel. 
The intermediate shaft assembly 23 is shown more clearly in FIGS. 2 and 3 
of the drawings and it comprises basically the pinion member 36 (see FIG. 
3) which is of elongated construction and which is slidably and rotatably 
supported in housing 24 by a needle bearing 37. The pinion member 36 at 
one end is formed with a plurality of elongated teeth 38 and at its other 
end it forms part of the manually operable clutching mechanism. 
The elongated teeth 38 on the pinion member 36 are at all times in driving 
engagement with the gear 25 on output shaft 26 and in one axial position 
of pinion member 36 the teeth 38 are also in driving engagement with the 
motor driven wormwheel 22 while in another axial position of pinion member 
36 the driving engagement with wormwheel 22 is disengaged to permit 
rotation of pinion member 36 and thereby output shaft 26 by manual means. 
The wormwheel 22 is provided with a steel insert or hub member 39 which is 
shown more clearly in the exploded view of FIG. 3 and which is mounted in 
wormwheel 22 and connected thereto by conventional means, such as the 
connecting bolts 40, as shown in FIG. 2. The hub member 39 has a central 
bore 41 adapted to receive pinion member 36 and at its pinion receiving 
end the bore 41 is enlarged to provide a number of equally spaced recesses 
42 which are elongated circumferentially around the bore as will be 
hereinafter explained. 
The other end of hub member 41 is formed with an axial extension 43 which 
is mounted within the inner race of a ball bearing 44 secured in housing 
24 by a keep plate 45. The end portion 46 of hub member 41 is screw 
threaded to receive a lock nut 47 for retaining hub member 41 and its 
wormwheel 22 in position. 
The end portion 48 of pinion member 36 is firstly of smooth configuration 
to fit snugly within the bore 41 of hub member 39. This part 48 of the 
pinion member 36 has no driving connection with the hub member 39 and is 
merely slidably and rotatably supported therein. Adjacent portion 48 the 
pinion member 36 is formed with a plurality for example, twelve elongated 
teeth 38, which as previously mentioned are in constant driving engagement 
with the spur gear 25 on output shaft 26. The ends of the teeth extend 
also into driving engagement with the wormwheel hub 39 but at this portion 
of the pinion member 36 the ends of some of the teeth are removed so as to 
leave a number, for example, four teeth only, shown by reference 38A (see 
FIG. 3). These extended teeth 38A project into corresponding recesses 42 
in hub member 39 so as to provide the necessary drive from the main 
wormshaft 15 to the output shaft 26 of the actuator when the pinion member 
36 is in its axial position as shown in FIG. 2. The recesses 42 comprise 
separate cut-outs each having a circumferential width greater than that of 
a corresponding tooth extension 38A on the pinion member. The arrangement 
permits more easy re-engagement on energisation of the motor drive, but in 
particular the arrangement enables a rotational backlash to be provided in 
the coupling which produces a hammer blow effect when the actuator is 
reversed. 
As previously mentioned the pinion member 36 is axially slidable in hub 
member 39 (to the right as viewed in FIG. 2) for disengaging the extended 
teeth 38A from the recesses 42 in the hub member so as to allow 
independent manual rotation of pinion member 36. 
This axial movement of the pinion member 36 is obtained by a lifting yoke 
which comprises diametrically located members 49 bearing on an annular 
shoulder 50 formed in pinion member 36 by an enlarged end portion 51 (see 
also FIG. 4). The bearing members 49 of the lifting yoke are moved by a 
yoke collar 52 attached as by screw 53 to a shaft 54 which extends 
externally of housing 24 for manual operation by hand lever 55 (see FIGS. 
2 and 5). 
The pinion member 36 of the intermediate shaft assembly is held in its 
manual position (with the extended teeth 38A disengaged from recesses 42 
in the hub member 39 of wormwheel 22) by a conventional hand/auto spring 
urged finger mechanism as shown in FIGS. 2 and 4. 
A rod 56 is attached at one end to bearing member 49 of the yoke assembly 
by pin 57. The rod 56 extends along pinion member 36 and at its other end 
it pivotally carries a latch member 58 which engages the adjacent surface 
of wormwheel 22. The latch member 58 is urged by a spring 59 to assume an 
upright position in line with rod 56 but is maintained in the position 
shown in FIG. 4 during normal motor operation of the actuator. In the 
event of axial movement of pinion member 36 upwardly as viewed in FIG. 4, 
rod 56 moves upwardly with the yoke assembly to permit latch member 58 to 
pivot to assume its upright position in line with rod 56 to thereby hold 
pinion member 36 in its upper manual position. 
Disengagement of the latch member 58 is effected on rotation of wormwheel 
22 by the subsequent energisation of motor 12 which enables the rod 56 to 
move downwardly to permit the return of pinion member 36 to its motor 
position by a spring assembly 60. 
The spring assembly 60 is located in a central bore 61 extending into 
pinion member 36 from its enlarged end portion 51. The spring of the 
spring assembly 60 seats at its ends on a pair of plug members 62 and 63 
respectively mounted in bore 61. Plug member 63 is slidable in bore 61 and 
is attached to rod 64 which extends slidably through plug member 62 as 
pinion member 36 moves axially. Plug member 63 is located in the open end 
of bore 61 and is rotatably supported by a bearing 65 carried by a plate 
66 secured by bolt 67 to end cover 68 attached to housing 24. 
The end cover 68 forms part of a transversely mounted handwheel gear box 
mechanism. As shown in FIG. 2 the enlarged end portion 51 of pinion member 
36 is formed with two or more spaced axially extending lugs or teeth 69 
which are adapted to engage drivably with corresponding lugs or teeth 70 
projecting axially from the side surface of a wormwheel 71 mounted in end 
cover 68. Wormwheel 71 is in driving engagement with a worm 72 on 
handwheel shaft 73 (FIG. 5) mounted in transverse housing 74. A handwheel 
75 is fitted externally to shaft 73 for manual operation of the actuator. 
The actuator as described above is normally driven by motor 12 to rotate 
output shaft 26 with the pinion member 36 of the intermediate shaft 
assembly 23 in its motor position as shown in FIG. 2 in which the extended 
teeth 38A are in driving engagement with the recesses 42 of the hub 39 of 
wormwheel 22. In order to effect a change to manual operation the lever 55 
is manually operated to lift pinion member 36 by the yoke assembly 49 
against the spring assembly 60 so as to disengage the extended teeth 38A 
from the recesses or cut-outs 42. The length of the extended teeth 38A is 
such that the teeth 38A are disengaged from the wormwheel hub before the 
lugs or teeth 69 are drivably engaged with the lugs or teeth 70 on the 
manually rotatable wormwheel 71. As the lugs or teeth 69 and 70 are 
drivably engaged the latch member 58 is able to assume its upright 
position in engagement with the stationary wormwheel 22 so as to hold the 
pinion member 36 in its manual uppermost position. In this position the 
output shaft can be independently rotated by handwheel 75 until motor 12 
is energised to release the latch mechanism. 
The housing 24 is completed by the provision of the usual electrical 
control box housing 76 and switches shown at 77.