Abstract:
A device 3 for indicating the operating state of a linear actuation valve (5) comprises a mounting plate (9) having a rectilinear slot (11) therein for slidably receiving a perpendicularly extending follower stem (6) fixed to a follower nut (4). The nut (4) is threaded on to the exterior of a sleeve (7) which is mounted for conjoint rotation with the hub of a hand wheel (2) of the linear actuation valve. Engagement of the follower stem (6) with the slot (9) prevents rotation of the nut (4) and provokes it to move axially relative to the sleeve (7). 
     The mounting plate (9) also includes means for fixing sensors (15) and (16) to the plate for detecting arrival of the follower stem (6) moving along the slot in either of two positions to be detected.

Description:
FIELD OF THE INVENTION 
     This invention relates to a device for the remote sensing of the operating state of a linear actuation valve, to show whether the valve is fully open or fully shut. 
     BACKGROUND OF THE INVENTION 
     This invention refers to a device which may be fitted, for example, between the valve wheel and the bonnet of a linear actuation valve, and is provided with sensors which will indicate whether valve is fully open or fully shut. 
     STATE OF THE ART 
     Owing to the ever-increasing growth of remote control systems meant to operate some kind of process, the need has been felt for various kinds of devices to indicate fundamental parameters for different sorts of equipment. As regards manually operated linear actuation shut-off or block valves, which valves are widely used in the flow of liquids, it is becoming important that the operating state of the valve--whether open or shut--be known at a remote location. 
     Various ways of dealing with this problem have been put forward. EP-A-369918 of Jan. 29, 1994 teaches the use of two coils concentrically fitted to the valve shutter, the first coil inducing a voltage in the second coil, in a direct relationship to the position of the valve shutter so as to enable the state of the valve to be correctly indicated. 
     This arrangement works well but one of its chief drawbacks is that there are a lot of mechanical and electrical parts, the manufacturing cost is high, and the large number of electrical parts make it more likely to break down. 
     U.S. Pat. No. 4,967,792 of Jan. 29, 1990 brings in the use of small magnetized parts fixed to the valve stem, together with a device fitted between the bonnet and the valve wheel and able to detect the magnetic field generated about such small parts when they pass close to sensors lying within the device. A signal is thereby generated to indicate the operating state of the valve, that is, whether it is open or shut. 
     This arrangement works well but is hampered by the fact that the valve stem has to be drilled, thereby diminishing the valve stem cross-sectional area, which may affect strength of stem at such points. 
     In contrast to this state of the art, the invention herewith applied for enables the operating state of a linear actuation valve to be easily indicated without having to make great changes into any of the original parts of the valve. 
     SUMMARY OF THE INVENTION 
     The object of the invention is to provide a device fitted between the bonnet and the wheel of a linear actuation valve so that the operating state, of said valve, i.e., whether open or shut, may be ascertained. 
     The device consists of a sleeve threaded on its outside, which is fitted to the hub of the linear actuation valve wheel together with a part screwed on to the sleeve, known as a follower, which has a stem fitted to its outside, referred to as follower stem; plus a plate fixed to the bonnet in which there is an oblong slot, in which the follower stem will slide, and two other groups of oblong slots into which sensors can be fitted to sense the approach of follower stem as it moves up and down, to remotely inform when valve is fully open or fully shut. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects and advantages of the invention will be more readily perceived from the following detailed description given, merely by way of example, with reference to the accompanying drawings, in which: 
     FIG. 1 is a front view of a linear actuation valve with the device of this invention for indicating valve operating state; 
     FIG. 2 is a side view of the linear actuation valve with the device of this invention; 
     FIG. 3 is a side view, as a detail of FIG. 2, showing details of the threaded sleeve and the follower; 
     FIG. 4 is a front view of the front plate of the device of this invention; 
     FIG. 5 is a front view of the threaded sleeve, the right hand side of the drawing showing a section and the left hand side an elevational view; 
     FIGS. 6a and 6b are a front view and a side view, respectively of the follower and the follower stem. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The ever growing move towards automation within industry in general has brought about the rise of technologies to deal with the various problems that emerge. As regards the plants for processing of fluids, a greater number of devices have been developed to control and supervise such processes, especially to supervise the progress so as to centralize information at one single spot for enabling work to be done more efficiently. For such tasks to be properly carried out much information on supervision and central parameters for processes is collected at several points and directed to an operation supervision and control center. 
     A basic kind of information needed for such plants to operate properly is the operating state of shut-off or block valves, i.e. whether they are open or shut. This sort of information can be is easily obtained from valves that have some kind of operating mechanism, whether they are control valves or just power operated block valves. However, manually-operated block valves require some sort of device adapted to ensure that their operating state can be sensed remotely. 
     This invention is meant to offer an easy and cheap answer for such problem. 
     FIGS. 1 and 2 show a linear operating valve (5) with a device (3) fitted on top of it, below the hand wheel (2) that operates the stem (1) of the valve (5). 
     The device (3) for indicating the operating state of a linear actuation valve consists of a front plate (9), shown in greater detail in FIG. 4, an externally threaded sleeve (7) shown in greater detail in FIG. 5, a part (4) hereinafter referred to as the follower nut, a follower stem (6) attached to the follower nut (4) as can be more easily seen in FIGS. 6A and 6B, and finally two sensors (15) and (16). 
     The threaded sleeve (7) slips easily over the stem (1) in that the inside diameter of the sleeve is bigger than outside diameter of the stem (1) of the linear actuation valve (5), thus enabling said stem (1) to enter the sleeve with a clearence, without damaging the threads of said stem. 
     The threaded sleeve (7) is fixed to the hub of the hand wheel so as to rotate together with it. In this embodiment the threaded sleeve is fitted to the bushing of the hub of the wheel (2) by means of bolts (not shown) extending through holes (17) in a collar (8) secured to the sleeve (7). It should be pointed out that other methods may be used for fitting the threaded sleeve (7) to the wheel (2). 
     The follower nut (4) is screwed on to threaded sleeve (7) and its follower stem (6) has one of its ends fitted to the follower nut (4) so the stem (6) is perpendicular to threaded sleeve (7). In this embodiment the stem end is threaded so as to be screwed into a threaded hole (14) in the follower nut (4), though other ways of fixing the follower stem (6) to the follower nut (4) may be adopted. 
     FIG. 2 is a side view of linear actuation valve (5) and of the device (3) and shows in greater detail the threaded sleeve (7), the follower nut (4) and follower stem (6). 
     The front plate (9) of device (3) has an oblong slot (11) in which the follower stem (6) slides, and has two other groups of slots (12) and (13) intended to enable sensors (15) and (16) to be mounted on the plate (9). The front plate (9) has also holes (10) intended for fixing it to bonnet of a valve such as valve (5) shown. 
     The way in which device (3) functions to indicate the operating state of a linear actuation valve (5) is quite simple. When the hand wheel (2) is turned to open or to shut the linear actuation valve (5), threaded sleeve (7) turns together with the rotating hand wheel (2) since it is joined to it. The follower nut (4) is driven by the rotating hand wheel (2), as is the follower stem (6) joined to the follower nut (4). However, since the follower stem (6) passes through the oblong slot (11) in the front plate (9), rotation of the assembly of follower nut (4) and follower stem (6) with the rotating hand wheel (2) is prevented by the front plate (9) as the follower stem (6) contacts either edge of the slot (11). 
     Being thus prevented from turning, the follower nut (4) is obliged to travel up or down within the threaded sleeve (7) depending on whichever way the hand wheel (2) is being turned to open or to shut the linear actuation valve (5). 
     In following the up or down travel of the follower nut (4), the follower stem (6) approaches sensors (15) or (16) whenever linear actuation valve (5) approaches the fully open or fully shut state. The sensors (15) and (16) are fitted to the front plate (9), by means of groups of slots (12) and (13). These groups of slots (12) and (13) are so designed as to enable the sensors (15) and (16) to be assembled at spots that are adjustable to be sufficiently close to follower stem (6) when the latter reaches the limits of its travel, that is topmost and bottommost limits, as the valve becomes fully open or fully shut. 
     According to the type of sensor employed it may be necessary to fit them in such a way that the follower stem (6) actually touches them. 
     Hence, when the follower stem reaches either end of its travel, the sensors (15) and (16) perceive this, and send a signal to some remote panel to show that the associated valve has become completely open or shut, as the case may be. 
     The sensors (15) and (16) may be of various kinds, for example mechanically operated ones that operate by contact with the follower stem (6), or electronical sensors where no kind of physical contact is needed, to give but two examples. 
     The linear actuation valve operating device described and claimed herein is quite easy to manufacture, since the materials and parts needed for it are easily found on the market. Besides, the device performs outstandingly, and no specialized staff are needed to install it or to maintain it. 
     The pitch of the threads on the shaft (1) may be the same as that of the external threads on the sleeve (7), but may instead be greater or smaller than it if reduction or magnification of the axial movement of the follower stem (6) relative to that of the valve shutter is required.