AU729236B2

AU729236B2 - Rotary mechanism limit sensing

Info

Publication number: AU729236B2
Application number: AU83231/98A
Authority: AU
Inventors: Patrick Joseph Byrne
Original assignee: Individual
Current assignee: Individual
Priority date: 1997-09-09
Filing date: 1998-09-09
Publication date: 2001-01-25
Anticipated expiration: 2018-09-09
Also published as: AU8323198A

Description

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

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT 4* Name of Applicant: PATRICK JOSEPH BYRNE Actual Inventor Address for service is: Patrick Joseph Byrne WRAY ASSOCIATES 239 Adelaide Terrace Perth, WA 6000 Attorney code: WR Invention Title: Rotary Mechanism Limit Sensing Details of Associated Provisional Application No(s): P09077 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 10 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 20 positions of the rotary actuator mechanism, where some degree of flow control is 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- It is also often the case that the valves of the type that the invention is concerned with, are located in corrosive environments. It is also an object of the invention to provide a sensor mechanism that readily lends itself to applications in corrosive environments, if required. Thus the sensor mechanism of the invention is also intended to be suitable for use in marine applications, such as in oil rigs.

Throughout the specification, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

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 having interference means to interfere with a switch mechanism, and the .actuator portion having locking means to lock the collar angularly relative to the circular shaft portion, wherein said switch mechanism is carried on a mounting member and the mounting member includes means to adjust the degree of 20 impingement of said switch mechanism relative to said interference means. 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. The locking means allows the angular position of the circular shaft portion (and hence the angular position of the rotary shaft) at which the switch mechanism is actuated, to be adjusted. The means to adjust the degree of impingement allows for fine tuning of the precise position of switch actuation to be adjusted, and can allow for the dwell of actuation of the switch mechanism to be adjusted (the angle of rotation of the circular shaft portion through which the switch mechanism is actuated or switched on/off).

-4- The interference means of 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.

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

*a The projection may comprise a cam lobe formed in the external periphery of the collar.

a* 15 In a typical embodiment, the sensor mechanism will have two collars located on 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.

oe a.

The collar is preferably formed as an aperture extending radially through a half round rod. The projection preferably includes a portion of round rod extending axially from said half round rod, with their circumferential portions being continuous. Thus it can be seen that the collar and projection may be formed from a single piece of round rod, with a flat portion being machined in a part thereof, from one end thereof.

In the case where there are two collars and actuators, the collars are arranged with their flat portions lying juxtaposed. This minimises the internal space required in the sensor mechanism, allowing the overall dimensions of the sensor mechanism to be minimised. It also allows the switch mechanisms to be positioned at identical elevations, simplifying the set up of the sensor mechanism.

The switch mechanisms are carried on a mounting member, as described above, but preferably the means to adjust the degree of impingement comprises an assembly formed by an externally threaded rod and internally threaded members. The simnplest and hence most preferred way of achieving the adjustability is to have the externally threaded rod mounted to material forming what is in effect the chassis of the sensor mechanism, and extending through the mounting member, while the internally threaded members comprise nuts which are placed on either side of the mounting member, and tightened to secure the mounting member rigidly thereto.

o• In a preferred arrangement, the mounting member includes a sleeve through which the externally threaded rod is received, to assist with holding the mounting member in correct alignment relative to the chassis.

The invention will now be described in the following description of two specific embodiments of limit switch units for a rotary shaft operated valves, made with reference to the drawings in which: Figure 1 is a perspective view of a sensor mechanism for detecting the position of a rotary actuated shaft, according to the first embodiment; Figure 2 is an exploded perspective view of the sensor mechanism illustrated in Figure 1; Figure 3 is a perspective view of a sensor mechanism for detecting the position of a rotary actuated shaft, according to the second embodiment; Figure 4 is a perspective view of a circular shaft portion utilised in the second embodiment; and, Figure 5 is a perspective view of a collar and projection assembly portion utilised in both embodiments.

-6- Referring to Figure 1, the embodiment is directed toward a sensor mechanism assembly in the form of a limit switch unit 11 for providing feedback to a control panel, to indicate the position of a valve having a rotary actuator in an oil rig installation. The limit switch unit 11 includes a chassis in the form of a base plate 17, a tubular casing 19, and a top cover plate 21 which together form a housing for the unit 11.

The tubular casing 19 has a bush 23 having an internal thread 25 formed therein, the bush 23 being welded to the tubular casing 19. The bush 23 serves to carry wiring through to the inside of the limit switch unit 11. The base plate 17 includes four apertures 27 for mounting the limit switch unit 11.

The base plate 17 includes two stand-offs 29, and two externally threaded stand-offs 31, the like stand-offs 29 and 31 respectively being arranged in diametrical opposition. The stand-offs 29 and 31 are welded to the base plate 17 and extend from the top thereof, into the inside of the tubular casing 19. The 15 stand-offs 29 and 31 each have holes 33 which are internally threaded, extending axially therealong, for 'receiving screws 35 which are intended to depend through holes 37 in the top cover plate 21.

The base plate 17, tubular casing 19, and top cover plate 21 together form a ";*•.fluid/water-tight housing, and to this end, the base plate 17 and top cover plate 20 21 each have an annular slot in each of which is carried an 0-ring 39 (visible only in the base plate 17 in Figure The tubular casing 19 includes two machined annular ribs 41 one at each outer edge of the tubular casing 19.

When the machined'annular ribs 41 are received in the annular slots in the base plate 17 and the top cover plate 21, and contacting against the o-rings 39, tightening the screws 35 which depend through the holes 37 into the threaded holes 33 in the stand-offs 29 and 31, results in the o-rings being compressed, and a seal being created. The screws 35 are each fitted with 0-rings 43, to seal the holes 37 in the top cover plate 21. The base plate 17, tubular casing 19, top cover plate 21, and screws 35 are all formed of stainless steel, thus the unit 11 -7is able to be utilised in corrosive environments. Indeed, it is recommended that all of the machined or otherwise punched parts of the unit 11 are formed of stainless steel, in order to prevent electrochemical corrosion.

The base plate 17 includes a central aperture around which is located a boss through which a circular shaft portion in the form of a rod 47 extends. The rod 47 includes a flat portion 49 to provide purchase when the unit 11 is connected to the shaft of a valve or the like. The boss 45 houses a delrin/acetal bush (not shown, through which the rod 47 extends. The bush is a constant diameter cylinder, and includes a circumferential slot for receiving an o-ring, to seal against the inside of the boss 45. Sealing of the rod 47 against the bush will be described later.

o. o The rod 47 has two switch actuators 51 (shown separately in Figure The switch actuators each have a collar portion 53 formed by an aperture 55 through which the rod 47 is received. The collar portion 53 includes a threaded hole 57 15 extending through from the flat half-round end 59 of the switch actuator 51 The threaded hole 57 receives a grub screw 61 for securing the collar portion 53 to 0: the shaft 39, thus securing each switch actuator 51 at the desired radial position relative to the rod 47.

The collar portion 53 is also provided with a flat surface 63. In practise, the two switch actuators 51 are mounted to the rod 47 with their flat surfaces 63 lying against each other. This minimises the axial internal length required within the unit 11, which can assist where space for fitting the unit 11 is not at a premium in existing installations where the unit is being retrofitted.

Each switch actuator 51 also includes a projection portion 65 formed by the round rod portion of the switch actuator 51. The circumference of the round rod portion in effect forms a cam lobe to interfere with the roller 67 to operate a microswitch 69. As can be seen in Figure 5, the switch actuators 51 can be -8machined from a single piece of rod, which for reasons set out above, is formed of stainless steel.

A mounting member in the form of a pressed stainless steel plate 71 is received over the stand-offs 29 and 31. The plate 71 has two sleeves 73 welded thereto which are received over the threaded stand-offs 31. The plate 71 has the two micro-switches 69 mounted thereto, in a position so that they can be actuated by the projecting portions 65 of the switch actuators 51. (One microswitch is provided for each switch actuator 5.1 in this embodiment, since the expected rotation of the rod 47 is 900) °10 Nuts 75 are located on the threaded stand-offs 31 to secure against the plate 71 and sleeves 73. Adjustment of the nuts 75 to a different elevational position and o re-tightening results.in the height of the plate 71 relative to the base plate being adjusted, and hence the degree of interference of the rollers 67 of the microswitches 69, with the projection portions 65 of the switch actuators 51 being S 15 adjusted. This assists with the factory and field set up of the units 11, and also can be used to set the operational dwell of the microswitches 69 in the unit 11.

o. •The limit switch unit 11 of this embodiment is envisaged for use in detecting two extremes in position of the rotary actuator of a valve, 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 pos.itioned-in a required extremes of position and the -angular disposition of the relevant switch actuators 51- is adjusted and the grub screws 61 tightened. Further fine adjustment may be achieved through adjustment of the height of the plate 71 relative to the base plate 17. It will be understood that both adjustment methods are interactive.

Wiring from microswitches 69 is connected to terminal block bases 77, which carry removable terminal blocks (as known in the electrical and electronic industry) allowing for easy connection and disconnection. One of the terminal block bases 77/terminal blocks is a four way connector, and has one of its leads -9connected to an earth terminal 79. The other is a three way connector. The adoption of a three way connector and a four way connector assists in identifying the correct connectors, ensuring that the microswitches are connected to the correct circuit.

The second embodiment shown in Figure 2 is identical to the first embodiment, except that a cylindrical status window 81 is mounted on top of the top cover plate 17. The status window has a cover 83 which seals the interior of the status window 81 from contamination. A cylinder 85 contained within the status window 81 carries status information pertaining to the valve, as required, such as the wording "OPEN" and "CLOSED". The cylindrical status window 81 is formed of polymethyl methacrylate (acrylic/perspex), and has part of its inner *e surface blanked off to obscure indicia on the cylinder 85 irrelevant to the status of the valve. In this embodiment, the rod 47 is extended through the top of the -top cover plate 17, and the cylinder 85 is secured thereto.

The rod 47 of the second embodiment is shown in Figure 4. The extended portion 87 includes a threaded hole 89 for receiving a screw to secure the cylinder 85. Also included is an annular recess 91 which houses an o-ring, which is accommodated within an aperture in the top cover plate, to seal the top cover plate where the rod 47 extends therethrough. In relation to the sealing of the rod 47 in the boss 45 referred to above in the discussion of the first embodiment, an annular recess 93 is provided to house an o-ring which is accommodated sealingly within the delrin/acetal bush. The delrin/acetal bush is located between annular recesses 95 which accommodate circlips 97. A washer 99 is provided between each circlip 97 and the delrin/acetal bush, to prevent abrasion of the delrin/acetal bush. The rod 47 in the first embodiment does not include an extended portion 87.

It should be appreciated that the scope of the invention is not limited to the particular embodiments described herein. It will be apparent to the skilled addressee that changes or modifications may be made without departing from the spirit and scope of the invention. As one example, in an alternative embodiment the microswitches may be replace by proximity sensors.

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Claims

1. A sensor mechanism for a rotary shaft of a valve or the like, the sensor mechanism having an actuator portion for securing to the rotary shaft 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 having interference means to interfere with a switch mechanism, and the actuator portion having locking means to lock the collar angularly relative to the circular shaft portion, wherein said switch 10 mechanism is carried on a mounting member and the mounting member includes means to adjust the degree of impingement of said switch mechanism relative to said interference means to allow the precise position of switch actuation to be adjusted, and to allow for the dwell of actuation of the switch mechanism to be adjusted if desired. :15

2. A sensor mechanism as claimed in claim 1 wherein the interference means of the collar includes a projection positioned to interfere with the switch mechanism.

3. A sensor mechanism as claimed in claim 1 or 2 wherein the locking means comprises a grub screw extending through the collar to interfere with the circular shaft portion.

4. A sensor mechanism as claimed in claim 2 or 3 wherein the projection comprises a cam lobe formed in the external periphery of the collar.

A sensor mechanism as claimed in any one of the preceding claims wherein the sensor mechanism will has two said collars located on the circular shaft portion, each said collar having a projection associated with a switch mechanism, where said collars are set up to detect opposed rotary shaft -12- positions corresponding to a valve being fully open and the valve being fully closed.

6. A sensor mechanism as claimed in any one of the preceding claims wherein the collar is formed as an aperture extending radially through a half round rod.

7. A sensor mechanism as claimed in claim 6 wherein the projection includes a portion of round rod extending axially from said half round rod, with their circumferential portions being continuous.

8. A sensor mechanism as claimed in any one of claims 2 to 7 wherein the 10 collar and projection are formed from a single piece of round rod, with a flat .portion being machined in a part thereof, from one end thereof.

9. A sensor mechanism as claimed in claim 7 or 8 wherein there are two collars S-and actuators, and the collars are arranged with their flat portions lying juxtaposed.

10. A sensor mechanism as claimed in any one of the preceding claims wherein the means to adjust the degree of impingement comprises an assembly formed by an externally threaded rod co-operating with internally threaded ~members.

11. A sensor mechanism as claimed in claim 10 wherein the externally threaded rod is mounted to material forming a chassis of the sensor mechanism, and the externally threaded rod extends through the mounting member, and the internally threaded members comprise nuts which are placed on either side of the mounting member, and tightened to secure the mounting member rigidly thereto in the required position to set the desired degree of impingement. -13-

12. A sensor mechanism as claimed in claim 10 or 11 the mounting member includes a sleeve through which the externally threaded rod is received, to assist with holding the mounting member in correct alignment relative to the chassis.

13. A sensor mechanism for a rotary shaft of a valve or the like, substantially as herein described with reference to the drawings. Dated this ninth day of September 1998. PATRICK JOSEPH BYRNE Applicant IWray Associates Perth, Western Australia Patent Attorneys for the Applicant o•