Claims:WE CLAIM:

1. A hybrid rotary valve actuator (100) comprising:
a linear to rotary motion conversion mechanism (115) having a rotatable shaft (122);
a cylindrical body (101) having two end covers (102);
a primary cylinder (103) and two secondary cylinders (104) adjacent on either side of the primary cylinder (103), each secondary cylinder (104) separated from the primary cylinder (103) by a fixed disc (105), each fixed disc (105) having an axial cavity (113),
wherein the primary cylinder (103) holds two primary pistons (114) and each secondary cylinder (104) holds a secondary piston (107) integrated with a piston rod (108), wherein each of the piston rods (108) is guided in the axial cavity (113) of the corresponding fixed disc (105),
wherein the primary cylinder (103) comprises a first chamber (103a) and a second chamber (103b), wherein the first chamber (103a) is formed between the two primary pistons (114) and a second chamber (103b) is formed outside the two primary pistons (114) within the primary cylinder (103),
wherein each of the secondary cylinders (104) comprises a first pocket (104a) and a second pocket (104b), wherein each of the first pocket (104a) is formed between the fixed disc (105) and the secondary piston (107) whereas each of the second pocket (104b) is formed between the secondary piston (107) and the end cover (102),
wherein the primary cylinder (103) comprises a first port (109) and a second port (110), wherein the first port (109) is directly connected to the first chamber (103a) and the second port (110) is connected to the second chamber (103b) through a duct (111), each of the first pocket (104a) of the secondary cylinders (104) comprises an inlet port (112), and
wherein a plurality of compression springs is mounted in each of the second pocket (104b) of the secondary cylinders (104).

2. The hybrid rotary valve actuator (100) of claim 1, wherein the linear to rotary motion conversion mechanism (115) is either a rack-pinion mechanism (124) or a scotch yoke mechanism (119).

3. The hybrid rotary valve actuator (100) of claim 1, wherein the plurality of compression springs is either nested springs (106) or cluster springs (123).

4. A method to operate a hybrid rotary valve actuator (100) comprising:

a linear to rotary motion conversion mechanism (115) having a rotatable shaft (122);
a cylindrical body (101) having two end covers (102);
a primary cylinder (103) and two secondary cylinders (104) adjacent on either side of the primary cylinder (103), each secondary cylinder (104) separated from the primary cylinder (103) by a fixed disc (105), each fixed disc (105) having an axial cavity (113),
wherein the primary cylinder (103) holds two primary pistons (114) and each secondary cylinder (104) holds a secondary piston (107) integrated with a piston rod (108), wherein each of the piston rods (108) is guided in the axial cavity (113) of the corresponding fixed disc (105),
wherein the primary cylinder (103) comprises a first chamber (103a) and a second chamber (103b), wherein the first chamber (103a) is formed between the two primary pistons (114) and a second chamber (103b) is formed outside the two primary pistons (114) within the primary cylinder (103),
wherein each of the secondary cylinders (104) comprises a first pocket (104a) and a second pocket (104b), wherein each of the first pocket (104a) is formed between the fixed disc (105) and the secondary piston (107) whereas each of the second pocket (104b) is formed between the secondary piston (107) and the end cover (102),
wherein the primary cylinder (103) comprises a first port (109) and a second port (110), wherein the first port (109) is directly connected to the first chamber (103a) and the second port (110) is connected to the second chamber (103b) through a duct (111), each of the first pocket (104a) of the secondary cylinders (104) comprises an inlet port (112),
wherein a plurality of compression springs is mounted in each of the second pocket (104b) of the secondary cylinders (104),
wherein the linear to rotary motion conversion mechanism (115) is coupled to the two primary pistons (114) of the hybrid rotary valve actuator (100) while a rotary valve is coupled to the rotatable shaft (122), and

wherein the method comprises:
deploying a valve (116) to allow a fluid to at least one of the first port (109) and the second port (110) of the primary cylinder (103) of the hybrid rotary valve actuator (100),
supplying the fluid at prescribed pressure, under a normal condition, to each of the first pocket (104a) of the secondary cylinders (104) through the corresponding inlet port (112), so as to load the plurality of compression springs and attain ‘stay-put’ position by allowing the fluid pressure balance the opposing force of the plurality of compression springs, thus positioning each of the piston rods (108) integrated with the corresponding secondary piston (107) in the two secondary cylinders (104), simultaneously supplying the fluid at prescribed pressure, to the first chamber (103a) of the primary cylinder (103) through the first port (109) using the valve (116) for an outward motion of the two primary pistons (114), as each of the primary pistons (114) move outward towards the corresponding fixed disc (105) due to increase in fluidic pressure, the fluid from the second chamber (103b) is vented out through the duct (111) to the second port (110), thus activating the linear to rotary motion conversion mechanism (115) to rotate the rotatable shaft (122),
supplying the fluid at prescribed pressure to the second port (110) of the second chamber (103b) of the primary cylinder (103) using the valve (116) for an inward motion of the two primary pistons (114), as each of the primary piston (114) move inwards away from the corresponding fixed disc (105) due to increase in fluidic pressure, the fluid is vented from the first chamber (103a) through the first port (109), thus activating the linear to rotary motion conversion mechanism (115) to rotate the rotatable shaft (122), and
releasing the plurality of pre-compressed compression springs, under an abnormal condition, when the fluid supply at prescribed pressure is unavailable during the outward or inward motion of the two primary pistons (114), thereby pushing each of the secondary pistons (107) integrated to the corresponding piston rod (108) in an inward direction, each of the piston rod (108) enter into the primary cylinder (103) through the corresponding axial cavity (113) further pushing the two primary pistons (114) inwards to activate the linear to rotary motion conversion mechanism (115) to rotate the rotatable shaft (122), causing the rotary valve to attain a ‘fail-safe’ state.

5. The method to operate the hybrid rotary valve actuator (100) of claim 4, wherein the ‘fail-safe’ state is attained by rotating the rotatable shaft (122) in clockwise direction due to the pushing of each of the secondary pistons (107) in the inward direction by releasing the plurality of pre-compressed compression springs.

6. The method to operate the hybrid rotary valve actuator (100) of claim 4, wherein the ‘fail-safe’ state is attained by rotating the rotatable shaft (122) in anticlockwise direction due to the pushing of each of the secondary pistons (107) in the inward direction by releasing the plurality of pre-compressed compression springs.

7. The method to operate the hybrid rotary valve actuator (100) of claim 4, wherein the ‘fail-safe’ state is a ‘fail-safe open’ state or a ‘fail-safe close’ state.

8. The method to operate the hybrid rotary valve actuator (100) of claim 4, wherein the valve (116) is a directional control valve.

9. The method to operate the hybrid rotary valve actuator (100) of claim 4, wherein the rotary valve is a ball valve, a plug valve, a butterfly valve or a damper.
, Description:Form 2
The Patent Act 1970
(39 of 1970)
&
The Patent Rules 3
Complete Specification
(See section 10 and rule 13)
Title of the Invention:
A HYBRID ROTARY VALVE ACTUATOR AND A METHOD TO OPERATE THEREOF

Applicant: Rotex Manufacturers And Engineers Private Limited
Nationality: Indian
Address: Manpada Road,
Dombivali (East) – 421 204,
Maharashtra, India

The following specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF INVENTION
[0001] The invention relates generally to valve actuators in fluid control systems, and particularly to a rotary valve actuator that drives a rotary valve to a safe state in an event of a fluid supply disruption or a power disruption.

BACKGROUND
[0002] Valves discussed here are utilized for controlling fluid flow. These valves are remotely operated using valve actuators. Rotary valves are operated using rotary valve actuators. Commonly known rotary valve actuators have rack-pinion, spiral-shaft, scotch yoke and chain-sprocket mechanism, whereby the linear action gets converted to rotary action.
[0003] The rotary valve actuators generally fall into two categories: a single-acting actuator which is also known as spring-return actuator, and a double-acting actuator. Single-acting actuators use spring force to achieve safe condition of a rotary valve in open or close position and only one side of a piston is pressurized by fluid to operate the rotary valve actuator. In other words, as the piston moves under the influence of the fluid pressure, for the outward movement, the spring mounted on the other side of the piston gets compressed, while the inward motion is obtained by the action of the spring on the piston. Over the repeated operation of the single-acting actuators, the spring force varies from minimum to maximum during one stroke of operation and so during the cyclic operation, the spring is subjected to ‘Fatigue’ under higher cyclic operation, reducing its life. The replacement of the springs is cumbersome and also increases the cost of ownership of the rotary actuator.
[0004] In double-acting actuators without springs, both sides of the actuator pistons are pressurized alternatively to operate the rotary valve. In other words, the outward motion is obtained by providing fluid supply from one side of the piston and the inward motion is obtained by providing fluid supply from the opposite side of the piston. However, during the failure in the fluid supply, the actuator attains ‘stay-put’ condition, wherein the piston halts at the same or last position and rotary valve takes the partial position i.e. partially close or open unlike single-acting actuators that brings the rotary valve to its initial position, either fully close or fully open when the main fluid supply fails.
[0005] Patent no. US4295630 addresses the same problem as stated above over the cyclic operation of the spring of the actuator. This patent describes a fail-safe actuator for hydraulic control system, wherein the fail-safe actuator senses a failure in the system that triggers a pre-compressed spring to release and operate the valve. The spring remains in the compressed position during the normal operation of the actuator and is released only when the abnormal condition is detected. This patent discloses two embodiments, wherein first embodiment describes a manually controlled valve incorporating the fail-safe actuator. The other embodiment is hydraulic control system utilizing the fail-safe actuator, where fail-safe actuator and a rotary actuator are two independent units that increase the cost of the assembly. This system needs complex modifications in order to attain ‘fail-safe open’ state or ‘fail-safe close’ state. This patent further discloses utilization of flexible cables that themselves may not withstand the cyclic force. In addition, this system needs sensors to detect the failure and operate the control valves and pilot valves. Thus, the solution to isolate the spring actuator from the normal actuation of the valve seems to be costlier than the cost of the springs under cyclic loading.
[0006] Therefore, there is a need of an economical and reliable arrangement that overcomes the shortcomings.

OBJECTIVES OF THE INVENTION
[0007] An objective of a present invention is to provide a rotary valve actuator that ensures a connected rotary valve is always in a definite position.
[0008] Another objective of the present invention is to provide the hybrid rotary valve actuator that operates a rotary valve to attain a ‘fail-safe’ state in an event of a main fluidic supply disruption or a power disruption.
[0009] Another objective of the present invention is to provide the rotary valve actuator that operates the rotary valve to attain a ‘fail-safe open’ state or a ‘fail-safe close’ state with minimal modification.
[0010] Another objective of the present invention is to eliminate a cyclic operation of springs by using the springs only when there is a disruption situation and subjecting the springs under constant loading rather than cyclic loading to enhance the life of springs.
[0011] Another objective of the present invention is to reduce a fluid consumption and thereby minimize carbon emission when compressed air is used as a fluid.
[0012] Yet another objective of the present invention is to provide a low cost and safe rotary valve actuator.

SUMMARY

[0013] Present invention is a hybrid rotary valve actuator comprising a cylindrical body having two end covers, a primary cylinder and two secondary cylinders adjacent on either side of the primary cylinder. Each secondary cylinder is separated from the primary cylinder by a fixed disc. Each fixed disc has an axial cavity. The primary cylinder holds two primary pistons and each secondary cylinder holds a secondary piston integrated with a piston rod. Each of the piston rods is guided in the axial cavity of the corresponding fixed disc. The primary cylinder comprises a first chamber and a second chamber. The first chamber is formed in between the two primary pistons whereas the second chamber is formed outside the two primary pistons within the primary cylinder. Each of the secondary cylinders holds a secondary piston and comprises a first pocket and a second pocket. The first pocket is formed between the secondary piston and the fixed disc whereas the second pocket is formed between the end cover and the secondary piston.
[0014] The primary cylinder comprises a first port and a second port. The first port is directly connected to the first chamber and the second port is connected to the second chamber through a duct. Each of the first pocket of the secondary cylinders comprises an inlet port. A plurality of compression springs are mounted in each of the second pocket of the secondary cylinders. The plurality of compression springs may be nested springs or cluster springs. The primary cylinder holds two primary pistons coupled to a linear to rotary motion conversion mechanism while a rotary valve is coupled to a rotatable shaft. The linear to rotary motion conversion mechanism may be a rack-pinion mechanism or a scotch yoke mechanism. The rotary valve is a ball valve, a plug valve, a butterfly valve or a damper.
[0015] A method to operate the hybrid rotary valve actuator involves deploying a valve to allow a fluid to at least one of the first port or the second port of the primary cylinder of the hybrid rotary valve actuator. The valve may be a directional control valve - a 5/2-way solenoid valve or a 4/2-way solenoid valve. Under a normal condition, the fluid is supplied at prescribed pressure to each of the first pocket of the secondary cylinders through the corresponding inlet port.
[0016] The plurality of compression springs are then loaded to attain ‘stay-put’ position by allowing the fluid pressure balance the opposing force of the plurality of compression springs. Thus, each of the piston rods integrated with the secondary pistons are positioned in the secondary cylinders. Simultaneously, the fluid at prescribed pressure is supplied to the first chamber of the primary cylinder through the first port using the valve for an outward motion of the two primary pistons. As each the primary pistons move outward towards the corresponding fixed disc due to increase in fluidic pressure, the fluid from the second chamber is vented out through the duct to the second port, thus activating the linear to rotary motion conversion mechanism to rotate the rotatable shaft.
[0017] For an inward motion of each of the primary pistons, the fluid at prescribed pressure is supplied to the second port of the second chamber of the primary cylinder using the valve. As each of the primary piston move inwards away from the corresponding fixed disc due to increase in fluidic pressure, the fluid is vented from the first chamber through the first port thus activating the linear to rotary motion conversion mechanism to rotate the rotatable shaft.
[0018] Under an abnormal condition, when the fluid supply at prescribed pressure is unavailable during the outward or inward motion of the two primary pistons, the plurality of pre-compressed compression springs is released. Each of the secondary pistons integrated to the corresponding piston rod is pushed in inward direction. Each piston rod enter into the primary cylinder through the corresponding axial cavity further pushing the corresponding primary piston inwards to activate the linear to rotary motion conversion mechanism, causing the rotatable shaft to rotate, thus the rotary valve attains a ‘fail-safe state’. The ‘fail-safe’ state is attained by rotating the rotatable shaft in clockwise direction or anti-clockwise direction.

BRIEF DESCRIPTION OF DRAWINGS
[0019] Figure 1A shows a sectional view of a generic hybrid rotary valve actuator illustrating a movement of primary pistons and secondary pistons during a normal condition.
[0020] Figure 1B shows a sectional view of the generic hybrid rotary valve actuator illustrating the movement of the primary pistons and the secondary pistons during an abnormal condition.
[0021] Figure 2 shows the hybrid rotary valve actuator coupled with a valve, a main fluid source and a block linear to rotary motion conversion mechanism.
[0022] Figure 3A shows the hybrid rotary valve actuator deploying a rack-pinion linear to rotary motion conversion mechanism illustrating an outward motion of the primary pistons and the secondary pistons during the normal condition in one embodiment.
[0023] Figure 3B shows the hybrid rotary valve actuator deploying the rack-pinion linear to rotary motion conversion mechanism illustrating an inward motion of the primary pistons and the outward motion of the secondary pistons during the normal condition.
[0024] Figure 4 shows the hybrid rotary valve actuator of Figures 3A-3B during the abnormal condition illustrating a ‘fail-safe close’ state of the rotary valve.
[0025] Figure 5A shows the hybrid rotary valve actuator deploying the rack-pinion linear to rotary motion conversion mechanism in a reverse configuration illustrating the outward motion of the primary pistons and the secondary pistons during the normal condition in another embodiment.
[0026] Figure 5B shows the hybrid rotary valve actuator deploying the rack-pinion linear to rotary motion conversion mechanism in the reverse configuration illustrating the inward motion of the primary pistons and the outward motion of the secondary pistons during the normal condition.
[0027] Figure 6 shows the hybrid rotary valve actuator of Figures 5A-5B during the abnormal condition illustrating a ‘fail-safe open’ state of the rotary valve.
[0028] Figure 7 shows the hybrid rotary valve actuator deploying a scotch yoke linear to rotary motion conversion mechanism.
[0029] Figure 8 shows cluster springs mounted in the hybrid rotary valve actuator.

DETAILED DESCRIPTION

[0030] The invention shall now be described with the help of drawings. It is to be expressly noted that several variations are possible around the invention and the drawings and description should not be construed to limit the invention in any manner whatsoever.
[0031] A hybrid rotary valve actuator, as per present invention, is used to operate rotary valves, for example, ball valves, butterfly valves, plug valves and a damper. The present invention shows the hybrid rotary valve actuator that combines the advantages of a single-acting actuator and a double-acting actuator into a single device.
[0032] Figure 1A, a hybrid rotary valve actuator (100) illustrates inward-outward motion of two primary pistons (114) and outward motion of two secondary pistons (107) in order to open or close the rotary valve (not shown in Figures) as indicated by the arrows, during a normal condition. Figure 1B, the hybrid rotary valve actuator (100) shows inward motion of the two primary pistons (114) and the two secondary pistons (107), indicated by the arrows, during an abnormal condition.
[0033] Figures 1A-1B, the hybrid rotary valve actuator (100) comprises a cylindrical body (101) with two end covers (102). The cylindrical body (101) is divided into three cylinders: a primary cylinder (103) and two secondary cylinders (104) adjacent on either side of the primary cylinder (103), each secondary cylinder (104) is separated from the primary cylinder (103) by a fixed disc (105), each fixed disc (105) having an axial cavity (113). The primary cylinder (103) holds two primary pistons (114) whereas each of the secondary cylinders (104) hold secondary piston (107). Each of the secondary pistons (107) is integrated with a piston rod (108), wherein each of the piston rods (108) is guided in the axial cavity (113) of the corresponding fixed disc (105).
[0034] The primary cylinder (103) consists of a first chamber (103a) and a second chamber (103b). The first chamber (103a) is formed between the two primary pistons (114) and the second chamber (103b) is formed outside the two primary pistons (114) within the primary cylinder (103). Each of the secondary cylinders (104) consists of a first pocket (104a) and a second pocket (104b). Each of the first pockets (104a) is formed between the fixed disc (105) and the secondary piston (107) whereas each of the second pockets (104b) is formed between the end cover (102) and the secondary piston (107).
[0035] Further, the primary cylinder (103) has two ports: a first port (109) and a second port (110). The first port (109) is directly connected to the first chamber (103a) of the primary cylinder (103) whereas the second port (110) is connected to the second chamber (103b) through a duct (111) of the primary cylinder (103). Each of the first pockets (104a) of the secondary cylinders (104) comprises an inlet port (112).
[0036] A plurality of compression springs are mounted in each of the second pocket (104b) of the secondary cylinders (104), wherein the plurality of compression springs is nested springs (106). The nested springs (106) have one or more springs fitted inside a larger spring. However, in place of nested springs (106), cluster springs (123) may also be deployed. The cluster springs (123) are a group of springs arranged in each of the second pockets (104b) to oppose the movement of each secondary piston (107), as shown in Figure 8. The primary cylinder (103) resembles the double –acting rotary actuator without springs, whereas each secondary cylinder (104) resembles single-acting rotary actuator.
[0037] Figure 2 as seen with Figure 1A, shows an assembly (200) comprising the hybrid rotary valve actuator (100) coupled to a linear to rotary motion conversion mechanism (115) and a rotatable shaft (122) in connection with a valve (116) and a main fluid source (117). A fluid at prescribed pressure, flowing from the main fluid source (117), is directly supplied to each of the first pocket (104a) through the corresponding inlet port (112) of the secondary cylinders (104) and to the first chamber (103a) or the second chamber (103b) of the primary cylinder (103) from the first port (109) or the second port (110) respectively through the valve (116). The linear to rotary motion conversion mechanism (115) includes any one of a rack-pinion mechanism (124) or a scotch yoke mechanism (119) (as seen in Figure 7). The valve (116) may be a directional control valve, wherein the directional control valve is a 5/2-way solenoid valve, a 4/2-way solenoid valve, et cetera.
[0038] All illustrations and explanation here below is with the rack-pinion mechanism (124) comprising two racks (120 or 120’) integrated to the two primary pistons (114) and a pinion (121) representing the linear to rotary motion conversion mechanism (115) and the 5/2-way solenoid valve (118) representing the valve (116) as seen in Figures 3A-6. However, in place of the 5/2-way solenoid valve (118), the 4/2-way solenoid valve may also be deployed.
[0039] The working of the hybrid rotary valve actuator (100) is explained under two conditions, normal condition and abnormal condition. Figures 3A-3B and Figures 5A-5B illustrates the working of the hybrid rotary valve actuator (100) under normal condition. The normal condition may be defined as the condition when a fluid supply at prescribed pressure is available to operate the hybrid rotary valve actuator (100). Thus, under normal condition, the fluid at prescribed pressure, is supplied to each of the first pocket (104a) of the secondary cylinders (104) through the corresponding inlet port (112) and alternatively to the first port (109) and the second port (110) to operate the rotary valve for a close position or an open position.
[0040] Figures 4 and 6 illustrate the working of the hybrid rotary valve actuator (100) under abnormal condition. The abnormal condition may be defined as the condition when the fluid supply at prescribed pressure is unavailable to operate the hybrid rotary valve actuator (100) or when there is a power disruption. Thus, under abnormal condition, the fluid supply at prescribed pressure is unavailable to each inlet port (112), first port (109) or the second port (110).
[0041] Figures 3A-4 illustrates first embodiment, an assembly (300) comprising the hybrid rotary valve actuator (100), wherein the rack-pinion mechanism (124) is coupled to the two primary pistons (114) of the hybrid rotary valve actuator (100) while the rotary valve (not shown in Figures) is coupled to the rotatable shaft (122), in addition with the main fluid source (117) and 5/2-way solenoid valve (118). Figure 3A as seen with Figure 1A, under the normal condition, the fluid is supplied at prescribed pressure, directly to each of the inlet port (112) of the secondary cylinders (104) from the main fluid source (117) as well as to the first port (109) of the primary cylinder (103) through the 5/2-way solenoid valve (118) to operate the rotary valve for the open position. Here, the first port (109) acts as a supply port. As the fluid pressure in each of the first pocket (104a) of the secondary cylinders (104) is increased, the corresponding secondary piston (107) displaces towards the end cover (102) thus compressing or loading the nested springs (106) and attain ‘stay-put’ position by allowing the fluid pressure balance the opposing force of the nested springs (106), thus positioning each of the piston rods (108) integrated with the corresponding secondary piston (107) in the secondary cylinder (104). Simultaneously, the fluid pressure in the first chamber (103a) increases, thus moving each primary piston (114) integrated with corresponding rack (120) outward towards the fixed disc (105) (as indicated in Figure), the fluid from the second chamber (103b) is exhausted through the duct (111) to the second port (110), in this case, the second port (110) acts as a vent port, thus activating the rack-pinion mechanism (124), causing the rotatable shaft (122) to rotate in an anti-clockwise direction for the open position of the rotary valve.
[0042] Figure 3B as seen with Figure 1A, under the normal condition, the fluid is supplied at prescribed pressure directly to each of the inlet port (112) of the secondary cylinders (104) from the main fluid source (117) as well as to the second port (110) of the primary cylinder (103) through the 5/2-way solenoid valve (118) to operate the rotary valve for a close position. Here, the second port (110) acts as a supply port. As the fluid pressure in the second chamber (103b) increases, the two primary pistons (114) integrated with the corresponding rack (120) move inwards away from each fixed disc (105) (as indicated in Figure), the fluid from the first chamber (103a) is exhausted through the first port (109), here the first port (109) acts as the vent port, thus activating the rack-pinion mechanism (124), causing the rotatable shaft (122) to rotate in a clockwise direction for the close position of the rotary valve.
[0043] Figure 4 as seen with Figure 1B and Figures 3A and 3B, under the abnormal condition, the fluid supply at prescribed pressure is unavailable to each of the inlet ports (112), the first port (109) or the second port (110) (as seen in dotted circles). In absence of the fluidic pressure to each of the first pocket (104a) of the secondary cylinders (104), the nested springs (106) which were loaded or compressed under the normal condition are released, pushing each of the secondary pistons (107) integrated to the corresponding piston rod (108) in inward direction as indicated by arrows. The corresponding piston rod (108) enters into the primary cylinder (103) through the axial cavity (113) further pushing the two primary pistons (114) integrated with the corresponding rack (120) inwards to activate the rack-pinion mechanism (124), causing the rotatable shaft (122) to rotate in the clock-wise direction for the close position of the rotary valve and attain a ‘fail-safe close’ state.
[0044] Figures 5A-6 illustrates another embodiment. The assembly (400) of Figures 5A-6 is similar to the assembly (300) of Figures 3A-4 as explained above, expect the two racks (120), here the two racks (120’) are disposed in a reverse configuration such that when the two racks (120’) move outward towards the corresponding fixed disc (105), the rotatable shaft (122) rotates in the clock-wise direction, whereas when the two racks (120’) move inwards away from the corresponding fixed disc (105), the rotatable shaft (122) rotates in the anti-clock wise direction.
[0045] Figure 5A as seen with Figure 1A, under the normal condition, the fluid is supplied at prescribed pressure, directly to each of the inlet port (112) of the secondary cylinders (104) from the main fluid source (117) as well as to the first port (109) of the primary cylinder (103) through the 5/2-way solenoid valve (118) to operate the rotary valve for a close position. Here, the first port (109) acts as a supply port. As the fluid pressure in each of the first pocket (104a) of the secondary cylinders (104) is increased, the corresponding secondary piston (107) displaces towards the end cover (102) thus compressing or loading the nested springs (106) and attain ‘stay-put’ position by allowing the fluid pressure balance the opposing force of the nested springs (106), thus positioning each of the piston rods (108) integrated with the corresponding secondary piston (107) in the secondary cylinders (104). Simultaneously, the fluid pressure in the first chamber (103a) increases, thus moving each primary piston (114) integrated with the corresponding rack (120’) outward towards the corresponding fixed disc (105) (as indicated in Figure), the fluid from the second chamber (103b) is exhausted through the duct (111) to the second port (110), in this case, the second port (110) acts as a vent port, thus activating the rack-pinion mechanism (124), causing the rotatable shaft (122) to rotate in the clockwise direction for the close position of the rotary valve.
[0046] Figure 5B as seen with Figure 1A, under the normal condition, the fluid is supplied at prescribed pressure directly to each of the inlet ports (112) of the secondary cylinders (104) from the main fluid source (117) as well as to the second port (110) of the primary cylinder (103) through the 5/2-way solenoid valve (118) to operate the rotary valve for an open position. Here, the second port (110) acts as a supply port. As the fluid pressure in the second chamber (103b) increases, each of the primary piston (114) integrated with the corresponding rack (120’) move inwards away from the fixed disc (105) (as indicated in Figure), the fluid from the first chamber (103a) is exhausted through the first port (109), here the first port (109) acts as the vent port, thus activating the rack-pinion mechanism (124), causing the rotatable shaft (122) to rotate in anti-clockwise direction for the open position of the rotary valve.
[0047] Figure 6 as seen with Figure 1B and Figures 5A-5B under the abnormal condition, the fluid supply at prescribed pressure is unavailable to each of the inlet ports (112), the first port (109) or the second port (110) (as seen in dotted circles). In absence of the fluidic pressure to each of the first pocket (104a) of the secondary cylinders (104), the nested springs (106) which were loaded or compressed under the normal condition are released, pushing each of the secondary pistons (107) integrated to the corresponding piston rod (108) in inward direction as indicated by arrows. The corresponding piston rod (108) enter into the primary cylinder (103) through the axial cavity (113) further pushing each of the primary piston (114) integrated with the corresponding rack (120’) inwards to activate the rack-pinion mechanism (124), causing the rotatable shaft (122) to rotate the rotary valve in the anti-clockwise direction for the open position and attain a ‘fail-safe open’ state.
[0048] Thus, the first port (109) and the second port (110) interchange their roles as supply port and vent port or vice versa in Figures 3A-3B and 5A-5B to alternatively open or close the rotary valve.
[0049] Thus, under the normal condition, as described in Figures 3A-3B and Figures 5A-5B, each of the secondary cylinders (104) remain un-functional and isolated from the primary cylinder (103) once the nested springs (106) are compressed, thus the nested springs (106) are under constant loading rather than the cyclic loading as described in the prior art. The nested springs (106), under the constant loading, will reduce its continuous compression and or release movement and enhance the life of the springs and reduce the energy required for compressing the nested springs (106) during each operating cycle. In addition, due to constant loading of the nested springs (106) in each of the secondary cylinders (104), the fluid consumption will be reduced and the full torque will be available for the operation of the primary cylinder (103) of the hybrid rotary valve actuator (100) to operate the rotary valve for open or close position. The reduction in fluid consumption will minimize the carbon emission when compressed air is used as fluid.
[0050] Under the abnormal condition, as described in Figures 4 and 6, each of the primary pistons (114) integrated with the racks (120 or 120’) and each of the secondary pistons (107) under the influence of nested springs (106) move inwards, positioning the rotary valve in ‘fail-safe’ state, that is in ‘fail-safe open’ state or ‘fail-safe close’ state as explained above.
[0051] As described in prior arts, to attain ‘fail-safe open’ state or ‘fail-safe close’ state the system needs complex modifications, whereas, in the present invention, minimal modifications are required only in the primary cylinder (103) of the hybrid rotary valve actuator (100) in order to attain the ‘fail-safe open’ and ‘fail-safe close’ state. The two secondary cylinders (104) do not require any modification. In other words, only the racks (120 and 120’) of the rack-pinion mechanism (124) in the primary cylinder (103) are disposed in reverse configuration in order to attain ‘fail-safe open’ state or ‘fail-safe close’ state.