CA1175564A - Valve position indicator and method - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Disclosed is a method of monitoring the extent of throttling a sliding gate teeming valve where a hydraulic ram is employed by measuring the fluid flow in and out of the hydraulic cylinder which drives a valve, either for throttling, or positioning. Shown is a hydraulic motor in series with the driving fluid with a rotary counter.
The rotation of the motor is read out remotely and preferably digitally, with intermediate means translating the volume of fluid flow into a calculation of travel of the hydraulic ram which, in turn can be translated into the movement of the sliding gate valve. Means for zero setting upon actuation are provided within the method. The apparatus shows the combination of an hydraulic-type motor in the hydraulic line which drives the actuating cylinders of a sliding gate valve. The rotation of the motor is then counted and calculated to read out in digital form, preferably electrically actuated and remote from the motor. A logic circuit is provided to be actuated by the read-out to compute the hydraulic fluid displacement and indicate the position of the valve. Means for gearing the motor and counter for each operation is further included in the combination.

Description

1175Sf~4 The present invention is directed primarily to indicating the position of a valve for controlling the teeming or flow of molten fluids, and more particularly the teeming of steel. It finds particular utility in valves such as exemplified in U.S. patent 4,063,668 and Reissue patent 27,237, and more particularly as modified for throttling of the subject exemplified valves as exemplified in Canadian Patent 1,103,921 and Canadian Patent 1,136,829.
The patents and patent applications identified above are directed to refractory-type sliding gate valves for controlling the flow or teeming of steel. The patent applications which are copending are directed to throttling in such valves where the sliding gate and the fixed gate are initially in register for full flow pour, and then the sliding gate is shifted in order to reduce the effective size of the pouring orifice.
In most applications the throttling as well as the movement of the sliding gate is accomplished by actuating hydraulic rams.
The operator normally monitors the flow of steel by watching the stream. It will be appreciated that in the high temperature and ~0 corrosive environments involved, the accuracy of such visual inspection of flow rates will depend heavily upon the skill and experience of the operator, and even with the most skillful operator, the accuracy and repeatability of the extent of throttling is empirical.
It is therefore desirable, particularly for purposes of repeatability and control, to have a means for accurately determining the position of such a valve, open, closed, and direction of open and close. In addition, where such a valve involves means for throttling, it is important to measure the extent of throttling, and to be able to repeat the same from pour-to-pour.
The present invention contemplates a method of monitoring the position of a sliding gate valve where a hydraulic actuator is :117~5~4 ] emp~ ~d by measuring the fluid flow in and out of the hydraulic actuator which drives the valve, either for throttling, or positioning.
Desirably the method includes inserting in series with the hydraulic actuator a fluid motor which drives a rotary sensor. The rotary sensor signal is read out remotely and preferably digitally, with intermediate means translating the volume of fluid flow sensed into distance of travel of the hydraulic actuator which, in turn, can be translated into the movement of the sliding gate valve. Means for zero setting upon actuation are provided within the method.
The apparatus contemplates primarily the combination of a fluid motor in the hydraulic line which drives the hydraulic actuator of a sliding gate valve. The rotation of the motor is then counted and calculated to read out remote from the motor and in digital form the position of the valve. A logic circuit is actuated by the read-out to compute the hydraulic fluid displacement and thus indicate the position of the valve. Means for zeroing the motor and counter for each operation is further included in the combination.
It is a primary object of the present invention to read accurately, and with repeatability, the position of the valve actuator 20 of a tundish or ladle gate valve thereby converting to the position of the valve. This permits the operator to observe open, closed, or extent of throttle.
A related object of the present invention looks to a method of remotely positioning an electrical digital read-out for measuring the position of a sliding gate valve and which will be in an environment that is more conducive to long life and accurate operation.
Still another object of the present invention is to provide a method and apparatus for reading the positions of a sliding gate valve when it is throttled, whereby automatic controls can be developed 30 for controlling the level of steel in both a ladle and a tundish in coordinated fashion for feeding a continuous caster.
Still another object of the present invention is to achieve the above objectives within the bounds of an economically advantageous unit.

l Further objects and advantages of the present invention will become apparent as the following description of an illustrative method and embodiment proceeds taken in conjunction with the accompanying drawings, in which:
FIG. 1 shows in perspective, partially diagrammatic view the environment of and read-out of the present indicator and method;
FIG. 2 is a partial block diagram showing the flow of hydraulic fluid and coupling of the same to the electrical read-out and counter;
FIG. 3 shows how FIGS. 3A, 3B and 3C are to be arranged for viewing;
FIGS. 3A, 3B and 3C together form a detailed schematic diagram of the circuit which converts the output of the rotary sensor to digital or analog display indicating valve position; and FIG. 4 is a diagrammatic phase diagram of some of the pulse relationships within the circuit.
The present method is based upon the proposition that where the movement of a valve is a ~unction of hydraulic fluid displacement, the valve being in a highly corrosive and high heat environment, the best way to read the valve position is to determine the amount of hydraulic fluid displaced in moving the valve. The method is well set forth in FIG. 2 where it will be seen that a directional valve 60 controls the movement of the hydraulic actuator. In most commercial applications a hydraulic cylinder or ram 61 is driven by a pump and tank 67, but the present invention also finds utility where a hydraulic motor is driven. All of the fluid displaced, whether the cylinder is single acting or double acting and whether the valve is single acting or double acting, passes through and drives a positive displacement fluid motor 62. The positive displacement fluid motor, in turn, drives a rotary sensor pulse generator 10 normally of the rotary type with an optical shaft encoder. For a typical 3 1/4" bore hydraulic cylinder which is stroked 3 1/2" in two seconds, the positive displacement fluid motor will rotate at 1,130 revolutions per minute which approximates 20 revolutions per second.

117~5~i4 1 The positive displacement fluid motor 62 drives an optical rotary shaft encoder 10 which generates two electrical signals, called the "Clock~ 63 and the "Second Clock" 64, each of which consists of 200 square wave pulses per motor revolution, and which are generated 90 out of phase. Thus when the encoder rotates clockwise the Clock lags the Second Clock and when the encoder rotates counterclockwise the Clock leads the Second Clock. Consequently the direction of valve 65 movement may be detected from the relative phase of the Clock and Second Clock by direction detector 68. Further, the 20 revolutions 10 per second times 2 seconds times 200 pulses per revolution delivers 8,000 pulses for 3~" of displacement. And any intermediate displacement can be calculated from the number of Clock pulses generated by movement to such intermediate displacement, including subtracting Clock pulses when the movement is reversed.
To accommodate for the lost motion, wind-up, or mechanical "slop~ in the valve upon change of direction of movement , an adjustable skip delay 69 is interposed in the circuit after the direction detection and before Clock pulse counting. The skip delay precludes the counting of any preselected number of Clock pulses (the number is determined 20 empirically for each particular valve). Once the direction detection and skip delay has been applied to the signal, it then proceeds into the multiply, count and divide circuit 70. The purpose of this circuit is to translate the number of pulses into the movement of the valve, taking into account the diameter of the cylinder and the length of stroke. Furthermore, the read-out can be made to be displayed on a light emitting diode display 66 in either millimeters, or inches such as shown in FIG. 1. In addition, a binary coded decimal output 72 is available to be sent to a screen for a graphic display of the valve position.
Separately, the method contemplates positioning a digital-to-analog converter 73 also in parallel with the other displays which can read the results of the position on a meter 74, as distinguished from digitially.

S~4 l Finally, the method also contemplates a pulse output terminal 75 prior to the divide and multiply circuitry movement to feed into automatic programming for further controlling the unit independently of manual operation. For example, where the level of steel in the mold for the continuous casting is constantly monitored, this information can be passed to the pulse output receiver, and upon noting a lowering in the level of the steel in the mold, the valve is told to open a finite distance until the level is reestablished. While this involves some electronic "hunting~ it takes place in so few milliseconds that 10 stabilization promptly occurs.
FIGS. 3, 3A, 3B, and 3C disclose the basic schematic diagram for a logic circuit which performs the method as set forth above.
More specifically, pulse generator 10 outputs the Clock 63 and the Second Clock 64 signals into the clock and data inputs, respectively, of dual D flip-flop 11. Flip-flop 11 may be an integrated circuit of type 7474. If the Second Clock is leading the Clock, then the Q
output 12 of flip-flop 11 will be high and the not-Q output 13 will be low; whereas if the Second Clock is lagging the Clock, then output 12 will be low and output 13 will be high. Thus flip-flop 11 detects the 20 direction of movement of the pulse generator 10 (and thus also of the valve being controlled), and this direction information is fed into binary-coded decimal arithmetic units 14-20 as follows: If output 13 is low, then the arithmetic units are put into the add mode; whereas if output 13 is high the arithmetic units are in the subtract mode.
The arithmetic units are integrated circuits of type 82S82, and the overflow from unit 14 feeds into unit 15; the overflow of unit 15 feeds into unit 16, etc.; so seven-digit counts are within the capacity of the circuit.
The Clock passes through OR-gate 51 for counting unless the 30skip delay prevents the passage through OR-gate 51. The skip delay is only active just after the direction of movement of the pulse generator changes, and is incorporated to account for lost motion, wind-up, or mechanical slop in the valve. The operation of the skip delay will be described later.

55~4 1 The counting of Clock pulses is as follows:
1. The Clock is fed into the load input of D flip-flops 21-27. The flip-flops may be integrated circuits of type 74175.
Because the output of the flip-flops is to be in engineering terms (i.e. inches or centimeters) the Clock pulses are not counted directly but rather are first multiplied by an appropriate factor, then counted.
For example, the previously computed generation of 8,000 pulses for the total 3~N movement by the hydraulic cylinder would be analyzed as follows: If arithmetic unit 20 and flip-flop 27 are to store the lO number of inches of movement, then arithmetic unit 18 and flip-flop 25 would be storing the number of hundredths of an inch of movement.
Because one-hundredth of an inch of movement will correspond to approx-imately 22.86 pulses (8,000 divided by 3.5 divided by 100) and because these 22.86 pulses are to result in 10,000 counts (arithmetic unit 18 and flip-flop 25 are the ten thousands' digit), each Clock pulse should produce 437 counts (10,000 divided by 22.86). These numbers are approximations; however, if greater accuracy is desired, then one has to add more arithmetic units and flip-flops so as to limit, in essence, the round-off error on this factor of 437. The multiplication 20 by 437 iS obtained by the wire jumper patterns 28-34. The 437 is set by connecting inputs 81, B2 and B4 of arithmetic unit 14 to the high line and input B8 to the low line (this represents 7), the B1 and B2 inputs of arithmetic unit 15 to the high line and inputs B4 and B8 to the low line (this represents 30), and input B4 of arithmetic unit 16 to the high line and inputs Bl, B2 and B8 to the low line (this represents 400), and all of the B inputs to arithmetic units 17-20 connected to the low line.

2. The multiplication of 437 presumes that the output 13 is low (so that the arithmetic units are in the addition mode) and that 30the flip-flops have been cleared (such as by the reset 36 or the start-up reset 37), the various inputs are as follows: The arithmetic units have Al,A2, A4 and A8 all low, and the Bl, B2, B4 and B8 as set by the wire jumper pattern. The arithmetic unit outputs Fl, F2, F4 " li75S~4 l an~ and C are the binary sums of the A's and B's, so Fl is the sum of A1 and Bl, F2 is the sum of A2 and B2 plus any overflow from F1, etc. The flip-flops have inputs D1, D2, D4 and D8 equal to the F1, F2, F4 and F8 outputs of the arithmetic units and the Q1, Q2, Q4 and Q8 outputs have been cleared to low. When the Clock goes high (i.e. a pulse) the flip-flops load the data at inputs D1, D2, D4 and D8 and it is stored and made available at the outputs Q1, Q2, Q4 and Q8 until the next time the Clock goes high (i.e. the next pulse). This stored data is just that provided by the wire jumper pattern; in particular, for arithmetic unit 14 the outputs prior to the first Clock pulse were F1, F2 and F4 all high and F8 low, thus upon the pulse the data stored and made available is Q1, Q2, Q4 all high and Q8 low. Because Q1, Q2, Q4 and Q8 are connected to A1, A2, A4 and A8, the arithmetic unit adds this to the wire jumper input at B1, B2, B4 and B8 and the sum appears at F1, F2, F4 and F8; thus after the first pulse the outputs Q1, Q2, Q4 and Q8 of the flip-flop are the same as the wire jumper input and the data at D1, D2, D4 and D8 is twice the wire jumper input. At the second time the Clock goes high (i.e. second pulse) this twice the wire jumper input will be loaded into the flip-flop and made available at the outputs Q1, Q2, Q4 and Q8, and additionally this output will be inputted at A1, A2, A4 and A8 to be added to the wire jumper input at B1, B2, B4 and B8, resulting in three times the wire jumper input appearing at the arithmetic unit outputs F1, F2, F4 and F8 and at the data inputs D1, D2, D4 and D8 of the flip-flop. In like fashion each time the Clock goes high (i.e. a pulse impinges on the flip-flop load input) another addition of the wire jumper input is made by loading the previous sum at D1, D2, D4 and D8 inputs into the flip-flop and thus inputting this sum to the arithmetic unit which adds another wire jumper input to it and outputs it to D1, D2, D4 and D8. Whenever an arithmetic unit overflows (i.e. contains more than nine) the overflow is passed on to the next arithmetic unit as an input to sum with the flip-flop stored and wire pattern inputs. The pin locations on arithmetic units 15-20 are analogous to those shown in arithmetic unit 14, and 1~755~4 locations on flip-flops 22-27 are analogous to those shown in flip-flop 21.

3. When the valve has reversed direction of movement, the output 13 will have put the arithmetic units into the subtract mode and for each count pulse the wire jumper input (i.e. 437) will be subtracted from the count total stored in the flip-flops, but otherwise the operation of the circuitry is analogous to add mode.

4. The data stored in, and the output of, flip-flops 25, 26 and 27 consists of a three-digit binary coded decimal which represents the millions, hundred thousands, and ten thousands of counts and which may be used to drive light-emitting diodes, analog devices, or any other mode of display.
The skip delay is used to provide for a predetermined number of Clock pulses to be ignored in the counting process each time the valve reverses direction. Such pulses presumably reflect motion by the hydraulic fluid without any movement by the valve itself and is termed lost motion, wind-up, or mechanical slop in the valve. The skip delay circuitry operates as follows:
1. Upon a change in direction of the pulse generator 10, the Clock and the Second Clock change relative phase and this is detected by flip-flop 11 and results in a change in the outputs 12 and 13. For example, if the pulse generator had been rotating clockwise, then the Second Clock had been leading the Clock and the output 12 will be high; upon a reversal of rotation direction, the Clock will now lead the Second Clock and the output 12 will drop to low.
Simultaneously the output 13 will change from low to high. Output 12 is the input for the one-shot multivibrator 37 which, upon a drop from high to low by output 12, generates a single pulse output which is inputted into OR-gate 39. Multivibrator 37 may be an integrated circuit of type 74121. The output 13, which changes from low to high, is inputted to one-shot multivibrator 38, which is identical to multivibrator 37. Because a change from low to high has no effect there is no output from multivibrator 38. If the change of the direction ~î~755~4 1 Of r~ Ition of the pulse generator 10 had been from counterclockwise to clockwise then output 12 would have changed from low to high and output 13 from high to low. In this event multivibrator 37 would have no output and multivibrator 38 would output a pulse into OR-gate 39.
Thus if direction is changed either from clockwise to counterclockwise or from counterclockwise to clockwise a pulse will be inputted to OR-gate 39 and thus a pulse will be outputted by OR-gate 39 into one-shot multivibrator 40. Multivibrator 40 is an integrated circuit of the same type and connections as one-shot multivibrator 37 and 10 outputs a pulse to OR-gate 41 and to one-shot multivibrator 42, which is also of the same type as multivibrator 37. The pulse into OR-gate 41 passes through and clears the three BCD up-down counters 43, 44 and 45. The BCD up-down counters may be integrated circuits of type 74192. The pulse from multivibrator 42 loads the preset digits in DIP
switches 46, 47 and 48 into the counters 43, 44 and 45. The counters' outputs are combined and fed into OR-gate 51 and AND-gate 49. As long as any of the counters 43, 44 and 45 contain any positive digit, the combined outputs will be high.
2. The Clock is fed into AND-gate 49 together with the 20 combined outputs of the counters 43, 44 and 45, so as long as the counters 43, 44 and 45 contain any positive digit the Clock will be transmitted through the AND-gate 49 and into counter 43 at the down input. Thus each pulse in the Clock will cause counter 43 to count down by one. Of course, counter 43 borrows from counter 44 and counter 44 in turn borrows from counter 45; thus as the Clock pulses are inputted into counter 43 the digits loaded from the DIP switches 46, 47 and 48 are counted down until counters 43, 44 and 45 all are reduced to zero, at which time the combined outputs of these counters drops from high to low. This drop from high to low turns off AND-gate 49 30 and also terminates the high inputted to OR-gate 51 continuously since the pulse generator 10 had changed direction of rotation. Thus for the first time since the change of direction the Clock passes through OR-gate 51 unaffected; whereas prior to the counting down by counters l 43 and 45, the output of OR-gate 15 had been a steady high and no counting of the Clock had occurred in the arithmetic units 14-20 and the flip-flops 21-27; this is illustrated in FIG. 4. Since the DIP
switches 46, 47 and 48 are adjustable, any predetermined number of Clock pulses may be ignored prior to counting starts. The number of such Clock pulses that are not to be counted is empirically determined, and depends upon the particular characteristics of the valve and hydraulic system involved.
Zero reset pushbutton 50 activates reset circuit 35 which clears all of the stored data in flip-flops 21-27 to zero, and thus also reduces to low the output which would be read on the light-emitting diode display as zero displacement.
Start-up reset circuit 36 comprises a a one-shot multivibrator which outputs one pulse when electrical power is first supplied to the system. This pulse is used to: (1) set flip-flop 11 into the mode with output 12 low and output 13 high; (2) clear BCD up-down counters 43, 44 and 45 to zero data and consequently low output; and (3) clear flip-flops 21-27 to zero data and consequently low output. Thus when the system is first activated the start-up reset circuit 36 aligns the system for use.
In summary, the logic circuit multiplies the pulses outputted from the pulse generator and counts the resultant multiplied pulses.
The count is outputted into display devices, such as light-emitting diode digital display. The logic circuit is also provided with a reset and start-up reset subcircuits to set the stored counts to zero for the beginning of the counting of the pulse generators output. Further, the logic CiLCUit is provided with a subcircuit which causes a preselected number of pulses from the pulse generator to not be multiplied and counted each time the pulse generator changes direction.

Claims (10)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. The method of reading the position of a sliding gate valve for controlling the flow of fluid comprising the steps of - utilizing a sliding gate valve in which an hydraulic actuator is employed for moving a refractory, - passing the fluid from at least one side of the hydraulic actuator through volume measuring means to determine the flow of fluid while the actuator is being moved from one position to another, - counting the volume reading of such hydraulic measuring device or its movement, - translating the count into a calculated sum to show the position of the movable refractory, - and displaying such position in a readable form.

2. In the method of claim 1 above, - providing means for zeroing the reading at positions of the movable refractory

3. In the method of claim 1 above, - providing means for preventing counting of pulses for a preselected number of pulses upon each change of direction of flow of said hydraulic fluid.

4. In a sliding gate valve for controlling the flow of fluid, a position indicator comprising, in combination, - hydraulic ram means for shifting at least one member of the sliding gate valve, - means for measuring the flow of hydraulic fluid to at least one side of said hydraulic ram means, - means for translating the reading of the flow of fluid to a remote location, - translation means for calculating the extent of motion of the movable refractory as related to the flow of hydraulic fluid, - and means for presenting a read-out of such movement of the movable refractory.

5. A valve position indicator for use with a movable refractory valve comprising, in combination, - hydraulic ram means for shifting at least one member of the sliding gate valve, - means for measuring the flow of hydraulic fluid to at least one side of said hydraulic ram means, - means for translating the reading of the flow of fluid to a remote location, - translation means for calculating the extent of motion of the movable refractory as related to the flow of hydraulic fluid, - and means for presenting a read-out of such movement of the movable refractory.

6. In the valve position indicator of claim 5 above, - additional means for zeroing the position indicator prior to shifting the refractory.

7. A sliding gate valve position indicator for use with a sliding gate valve with hydraulic actuator means for shifting the gate of said valve, comprising, in combination, - means for measuring the flow of hydraulic fluid driving said hydraulic actuator means, - means for translating the output of said means for measuring into the position of said gate, and - means for displaying the output of said means for translating.

8. The position indicator defined in claim 7, wherein - said means for measuring comprises a fluid motor connected in series on the hydraulic fluid line which drives said hydraulic actuator.

9. The position indicator defined in claim 8, wherein said means for translating comprises - a source of electrical power, - a rotary electrical pulse generator driven by said fluid motor, - a pulse counter to count the pulses generated by said pulse generator, and - means for correlating said pulse count with the position of said gate.

10. The position indicator defined in claim 9, further comprising - means for preventing counting of pulses for a preselected number of pulses upon each change of direction of flow of said hydraulic fluid, whereby lost motion, wind-up or mechanical stop is compensated for.