GB2094481A - Valve position indicator and method - Google Patents

Abstract

A method of monitoring the extent of throttling a sliding gate teeming valve 65 where a hydraulic ram 61 is employed measures the fluid flow in and out of the hydraulic cylinder which drives a valve, either for throttling, or positioning. A hydraulic motor 62 is in series with the driving fluid circuit and has a rotary counter 10. The rotation of the motor is read out remotely, e.g. 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. <IMAGE>

Description

SPECIFICATION Valve position indicator and method The present invention relates to a method and apparatus for indicating the position of the gate in a hydraulically-actuated sliding gate valve.

Throttling as well as the opening and closing movement of the sliding gate may be accomplished by actuating hydraulic rams. The operator normally monitors the flow through the valve by watching the stream. It will be appreciated that in the high temperature and corrosive environments involved in the teeming of steel, 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 skilful 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.

According to the present invention, there is provided a method of indicating the position of a sliding gate valve in which a hydraulic actuator is employed for moving a refractory gate, comprising passing hydraulic fluid from at least one side of the hydraulic actuator through a volume measuring device to determine the flow of fluid while the actuator is being moved from one position to another, counting the volume reading of the volume measuring device, translating the count into a calculated sum to show the position of the movable refractory gate, and displaying such position in a readable form.

The invention also provides 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 means for measuring the flow of hydraulic fluid driving said hydraulic actuator means, means for translating the output of said measuring means into the position of said gate, and means for displaying the output of said translating means.

The invention is further described by way of example, with reference to the accompanying drawings, in which: Figure 1 shows in perspective, partially diagrammatic view the environment of the readout of the present indicator and method; Figure 2 is a partial block diagram showing the flow of hydraulic fluid and coupling of the same to the electrical read-out and counter; Figure 3 shows how figures 3A, 3B and 3C are to be arranged for viewing; Figures 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 Figure 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 function 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 Figure 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 utiiity 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.

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 900 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 per second times 2 seconds times 200 pulses per revolution delivers 8,000 pulses for 3 2111 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 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 Figure 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 digitally.

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 moid 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 eiectronic "hunting" it takes place in so few milliseconds that stabilization promptly occurs.

Figures 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 1 2 of flip-flop 11 will be thigh and the not-Q output 1 3 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 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 1 4'20 as follows: If output 13 is low, then the arithmetic units are put into the add mode; whereas if output 1 3 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 1 5; the overflow of unit 1 5 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 skip 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.

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 2111 movement by the hydraulic cylinder would be analyzed as follows: If arithmetic unit 20 and flip-flop 27 are to store the number of inches of movement, then arithmetic unit 1 8 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 approximately 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 1 8 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 by 437 is obtained by the wire jumper patterns 28-34. The 437 is set by connecting inputs B1, 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 1 5 to the high line and inputs B4 and B8 to the low line (this represents 30), and input B4 of arithmetic unit 1 6 to the high line and inputs B1, 82 and 88 to the low line (this represents 400), and all of the B inputs to arithmetic units 1 7-20 connected to the low line.

2. The multiplication of 437 presumes that the ouput 13 is low (so that the arithmetic units are in the addition mode) and that the flip-flops have been cleared (such as by the reset 36 or the startup reset 37), the various inputs are as follows: The arithmetic units have Al, A2, A4 and A8 all low, and the B1, 82, B4 and B8 as set by the wire jumper pattern. The arithmetic unit outputs F1, F2, F4 and F8 and C are the binary sums of the A's and B's, so F1 is the sum of A1 and B 1, F2 is the sum of A2 and 82 plus any overlow from Fl , 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 Q1,02, 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 Dl, D2, D4 and D8 and it is stored and made available at the outputs Q1, 02, Q4 and Q8 until the next time the Clock goes high (i.e. the next puise). This stored data is just that provided by the wire jumper pattern; in particular, for arithmetic unit 14 4 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 01, Q2, Q4 ail high and 08 low.

Because 01, Q2, Q4 and Q8 are connected to Al, A2, A4 and A8, the arithmetic unit adds this to the wire jumper input at B1, B2, 84 and B8 and the sum appears at F1, F2, F4 and F8; thus after the first pulse the outputs 01, 02, 04 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 01, Q2, Q4 and Q8, and additionally this output will be inputted at Al , 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--2(i are analogous to those shown in-arithmetic unit 14, and the pin 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 1 3 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, flipflops 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 flipflop 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 1 3, 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 of rotation fo the pulse generator 10 had been from counterclockwise to clockwise then output 1 2 would have changed from low to high and output 1 3 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 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 ANDgate 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 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 ioaded 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 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 43, 44 and 45, the output of OR-gate 1 5 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 Figure 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 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 1 2 low and output 1 3 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 date 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 lightemitting 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 circuit 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 (11)

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

2. A method as claimed in claim 1, including for zeroing the volume reading at each additional pour or activation of the movable refractory gate.

3. A method as claimed in claim 1 or claim 2, including preventing counting of the volume reading for a preselected volume upon each change of direction of flow of said hydraulic fluid.

4. 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 means for measuring the flow of hydraulic fluid driving said hydraulic actuator means, means for translating the output of said measuring means into the position of said gate, and means for displaying the output of said translating means.

5. A position indicator as claimed in claim 4, in which said means for measuring comprises a fluid motor connected in series with said hydraulic actuator.

6. A position indicator as claimed in claim 5, in which said means for translating comprises 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.

7. A position indicator as claimed in claim 6, including means for preventing counting of pulses for a preselected number of pulses upon each change of direction of flow of said hydraulic fluid.

8. A position indicator as claimed in any one of claims 5 to 7 including means for zeroing the position indicator prior to shifting the gate.

9. A method of indicating the position of a sliding gate valve, substantially as hereinbefore described with reference to the accompanying drawings.

10. A method of indicating the position of a sliding gate valve in which an hydraulic actuator is employed for moving a refractory gate, comprising passing hydraulic fluid from at least one side of the hydraulic actuator through a volume measuring device to measure the flow of fluid while the actuator is being moved from one position to another, translating the measured flow into a calculated sum representative of the position of the movable refractory gate, and displaying such position in a readable form.

11. A sliding gate valve position indicator constructed and adapted to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.