AU714426B2

AU714426B2 - Rotary mechanism limit sensing

Info

Publication number: AU714426B2
Application number: AU16340/97A
Authority: AU
Inventors: Patrick Joseph Byrne
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-03-15
Filing date: 1997-03-14
Publication date: 2000-01-06
Anticipated expiration: 2017-03-14
Also published as: AU1634097A

Description

P/00/011 28/5/91 Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT

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Name of Applicant: Actual Inventor(s): Patrick Joseph Byrne Patrick Joseph Byrne Address for service is: WRAY ASSOCIATES 239 Adelaide Terrace Perth, WA 6000 Attorney code: WR Invention Title: "Rotary Mechanism Limit Sensing" Details of Associated Provisional Application No(s): PN8749 The following statement is a full description of this invention, including the best method of performing it known to me:- -2- The present invention relates to arrangements for limit sensing in rotary apparatus. The present invention provides a sensor mechanism for limit sensing for a rotary actuator mechanism, for use in process control, status sensing or status monitoring.

In chemical processing plants there is often a requirement for operation of valves to control the discharge of fluids. Typical industrial valves are actuated through a rotary actuator mechanism, not unlike that utilised for a domestic water tap or faucet. One major difference with the industrial valve is the degree of angular movement of the rotary actuator mechanism between conditions corresponding to the valve being fully closed and fully open is often only 900, although this angle may vary depending upon the particular valve concerned.

There is often a requirement, particularly where it is desired to automate the plant, to monitor or control movement of the rotary actuator mechanism of the valve. The simplest method of achieving this is to detect the angular position of 15 the rotary actuator mechanism, in order to provide feedback to control mechanisms or status indicators. Detection of movement of the rotary mechanism can be readily achieved by utilising microswitches which are actuated when the rotary actuator mechanism is at or reaches extremes of position. This method can be further extended to detecting intermediate S 20 positions of the rotary actuator mechanism, where some degree of flow control is o required.

This invention seeks to provide a sensor mechanism for a rotary actuator mechanism that may be readily set up, and provides a precise determination of any predetermined position of the rotary actuator mechanism, once set up.

This invention also seeks to provide a sensor mechanism which may be utilised on different rotary actuator mechanisms having different relative positions which need to be sensed.

-3- In accordance with the invention there is provided a sensor mechanism having an actuator portion for securing to a rotary shaft of a valve or the like, for rotary movement therewith; the actuator portion including a circular shaft portion about which is concentrically mounted a collar having an internal periphery conforming substantially to the external periphery of the circular shaft portion, the collar being adapted to interfere with a switch mechanism, and the actuator portion having locking means to lock the collar angularly relative to the circular shaft portion. The collar may completely encircle the circular shaft portion of the actuator portion, although this is not essential, providing that the collar cannot fall away from the circular shaft portion.

oooo The collar preferably includes a projection positioned to interfere with the switch mechanism. To calibrate the sensor mechanism, the sensor mechanism should *first be connected to the rotary shaft of the valve, and the rotary shaft moved to a position corresponding to the position which it is desired that the sensor mechanism should detect. If the rotary shaft is only to rotate to the point to be detected, setting up is quite straight forward. The collar is rotated about the circular shaft portion of the actuator portion so that the projection meets and actuates the switch mechanism, and then the locking means is employed to lock the collar relative to the circular shaft portion of the actuator portion.

*20 The locking means most preferably comprises a grub screw extending through the collar to interfere with the circular shaft portion.

The projection may comprise a cam lobe formed in the external periphery of the collar. The simplest and hence most preferred form of projection however, comprises a domed in-hex headed screw, which actuates the lever of a microswitch. If an intermediate position is desired to be detected, such an in-hex headed screw may be adjusted so that the microswitch is actuated at the intermediate position. Similarly, the adjustment of the in-hex headed screw relative to the collar allows for fine adjustment of the position of the shaft at which a microswitch is actuated.

-4- In a typical embodiment, the sensor mechanism will have two collars located on the circular shaft portion, each having a projection associated with a switch mechanism, where the collars are set up to detect opposed rotary shaft positions corresponding to a valve being fully open and the valve being fully closed.

The invention will now be described in the following description of one specific embodiment in the form of a limit switch unit for a rotary shaft operated valve, made with reference to the drawings in which: Figure 1 is a plan elevation from above of a shaft and collar assembly for a sensor mechanism in the limit switch unit of the embodiment; Figure 2 is a plan elevation from below of the shaft and collar assembly ~illustrated in figure 1; Figure 3 is a side elevation through aspect A-A of the shaft and collar "assembly illustrated in figure 1; Figure 4 is a side elevation through aspect B-B of the shaft and collar assembly illustrated in figure 1; Figure 5 is a exploded view of the shaft and collar assembly illustrated in figures 1 to 4; Figure 6 is a perspective view from above of the limit switch unit for a S•rotary valve incorporating the sensor mechanism illustrated in figures 1 to Figure 7 is a perspective view from below of the limit switch unit illustrated •in figure 6; Figure 8 is an exploded side elevation of the limit switch unit illustrated in figures 6 and 7; Figure 9 is a perspective exploded view of the limit switch unit illustrated in figure 8; Figure 10 is a plan view of the base plate and sensor mechanism of the limit switch unit illustrated in figure 9, showing the sensor mechanism in a non sensing intermediate position; Figure 11 is a plan view of the base plate and sensor mechanism of the limit switch unit illustrated in figure 9, showing the sensor mechanism in a first sensing position; li^liillll-i 1~1 Figure 12 is a plan view of the base plate and sensor mechanism of the limit switch unit illustrated in figure 9, showing the sensor mechanism in a second sensing position; and Figure 13 is a side elevation showing the limit switch unit, an associated actuator, and a valve.

Referring to figure 13, the embodiment is directed toward a limit switch unit 11 (shown separately in figures 6 and 7) for providing feedback to a pneumatic actuator 13 for the control of a valve 15 having a rotary actuator. The limit switch unit 11 includes a circular base plate 17 and a hemispherical cover 19 which together form a housing for the unit 11. The base plate 17 has two stand- 0**s offs 21 extending from the top of the base plate toward the inside of the cover 19. The stand-offs 21 each have threaded holes 23 extending axially therealong, for receiving bolts 24 which are intended to depend through holes in the top of the cover 19.

The base plate 17 and cover 19 together form a water-tight housing, and to this the base plate 17 has an annular slot 27 for receiving an o-ring, and also the machined annular rib 29 on the outer edge of the cover 19. When the *machined annular rib is received in the annular slot 27, tightening the bolts which depend through holes 25 into the stand-offs 21 results in the o-ring being 20 compressed, and a seal being created. The bolts should also be fitted with seals, suitably in the form of o-rings, to seal the joint with the cover 19. There is an annular step 31 located on the rear of the base plate 17, for receiving an oring, to seal the limit switch unit from the rear. The base plate 17 and cover 19 are formed of stainless steel, thus the unit 11 is able to be utilised in corrosive environments. Apertures 32 are provided to allow the unit 11 to be bolted to the pneumatic actuator 13.

The base plate 17 includes a central aperture 33 through which an actuator portion 35 may connect to the shaft of the pneumatic actuator 13. Referring to figures 1 to 5, the actuator portion 35 has an outwardly extending annular step 37 at its base, and includes a circular shaft portion in the form of a shaft 39 on -6which are located for rotation, two collars 41 and 43. Each collar 41, 43 includes a grub screw 45, 47 for securing the respective collar 41, 43 to the shaft 39.

Each collar 41, 43 also includes a projection in the form of an in-hex headed bolt 49 and 51, each having a rounded head.

The base plate 17 has a pair of micro-switches 53 and 55 mounted thereto, in a position so that the actuating levers 57 and 59 thereof can interfere with the bolts 49 and 51 on the collars 41 and 43 (respectively). The base plate 17 also includes a conduit 61 for carrying the wiring for the micro-switches.

The shaft 39 includes an axial bore 63 of receiving the shaft of a valve actuator 10 13. At the terminating end of the axial bore 63 is a diametric bar, which is received in a corresponding slot in the shaft of the valve actuator 13. This serves to maintain alignment of the unit 11. It will be appreciated that other methods may be utilised to maintain the alignment of the unit 11 relative to the actuator 13, which will depend to a large extent on the configuration of the 15 actuator, which in this instance is a pneumatic type manufactured by Keystone, U. Sand sold under the trade mark MORIN, and identified as model M72DA.

*o.The limit switch unit 11 of this embodiment is envisaged for use in detecting two extremes in position of the rotary actuator of the valve 15, corresponding to fully open and fully closed.. Setting up of the unit 11 is quite straight forward. The rotary actuator of the valve 15 is positioned in a required extremes of position and the angular disposition of the relevant collar is adjusted and the grub screw tightened.

Referring to figures 11 and 12, assuming figure 11 corresponds to a fully closed position of the valve, and figure 12 corresponds to a fully open position of the valve, operation of the unit 11 will now be described. Should process control determine that the valve needs to be opened, the pneumatic actuator 13 will be operated to open the valve, rotating the actuator portion 35 to the position shown in figure 12, so that microswitch 53 is actuated. Wiring from microswitch 53 is connected to control circuitry (not shown) which may be set to over-ride control -7of the pneumatic actuator 13. Conversely, should process control determine that the valve needs to be closed, the pneumatic actuator 13 will be operated to close the valve, rotating the actuator portion 35 to the position shown in figure 11, so that microswitch 55 is actuated. Wiring from microswitch 55 is also connected to control circuitry (not shown) which may also be set to over-ride control of the pneumatic actuator 13. Alternatively, signals derived from the switches may be used to provide remote status monitoring, or operate pumps or other equipment.

It should be appreciated that the scope of the invention is not limited to the particular embodiment described herein.

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Claims

1. A sensor mechanism having an actuator portion for securing to a rotary shaft of a valve or the like, for rotary movement therewith; the actuator portion including a circular shaft portion about which is concentrically mounted a collar having an internal periphery conforming substantially to the external periphery of the circular shaft portion, the collar being adapted to interfere with a switch mechanism, and the actuator portion having locking means to lock the collar angularly relative to the circular shaft portion.

2. A sensor mechanism as claimed in claim 1 wherein the collar completely 10 encircles the circular shaft portion of the actuator portion.

3. A sensor mechanism as claimed in claim 1 or 2 wherein the collar includes a projection positioned to interfere with the switch mechanism. A sensor mechanism as claimed in any one of the preceding claims wherein the locking means comprises a grub screw extending through the collar to 15 interfere with the circular shaft portion. C A sensor mechanism as claimed in claim 3 or 4 wherein the projection comprises a cam lobe formed in the external periphery of the collar. C

6. A sensor mechanism as claimed in claim 3 or 4 wherein the projection comprises a domed in-hex headed screw, which actuates the lever of a microswitch.

7. A sensor mechanism as claimed in claim 6 wherein said in-hex headed screw is adjustable relative to said collar to allow fine adjustment of the position at which the microswitch is actuated.

8. A sensor mechanism as claimed in any one of claims 3 to 7 wherein said circular shaft portion has two collars located thereon, each collar having a -9- projection associated with a switch mechanism, where the collars are set up to detect opposed rotary shaft positions corresponding to a valve being fully open and the valve being fully closed.

9. A sensor mechanism substantially as herein described with reference to the drawings. Dated this FOURTEENTH day of MARCH 1997. PATRICK JOSEPH BYRNE Applicant Wray Associates Perth, Western Australia Patent Attorneys for the Applicant ee 0