US3195111A - Mechanical storage apparatus for controlling periodic processes - Google Patents

Description

y 3, 1965 J. KUNKEL 3,195,111

MECHANICAL STORAGE APPARATUS FOR CONTROLLING PERIODIC PROCESSES Filed May 22, 1962 4 Sheets-Sheet l J U rge n Kunkefi INVENTOR.

AGENT.

July 13, 1965 J. KUNKEL 3,195,111

MECHANICAL STORAGE APPARATUS FOR CONTROLLING Filed May 22, 1962 PERIODIC PROCESSES 4 Sheets-Sheet 2 JU rg en Kunkei INVE NTOR.

July 13, 1965 J. KUNKEL 3,195,111

MECHANICAL STORAGE APPARATUS FOR CONTROLLING PERIODIC PROCESSES Filed May 22, 1962 4 Sheets-Sheet 3 FIG.3 50 I v I Jijrgen Kunkel INVENTOR BY garl g $955 A G E NT.

y 13, 1965 J. KUNKEL 3,195,111

MECHANICAL STORAGE APPARATUS FOR CONTROLLING PERIODIC PROCESSES Filed May 22, 1962 4 Sheets-Sheet 4 Jijrgen Kunkel INVENTOR.

BY Wt (R115;

A GE NT.

United States Patent H 4 13 Claims. (Cl. 340-173) My present invention relates to apparatus for controlling periodic processes and, more particularly, to a control system including mechanism for recording a periodically variable parameter.

In the commonly assigned copending application Ser. No. 55,347, now Patent No. 3,100,699 filed September 12, 1960, Von Bogdandy et al. have disclosed a feedbackoperated control system for periodic processes, especially for the operation of a refining furnace, wherein an output variable subject to both long-term and short-term variations is stabilized.

As pointed out in that application, a rotary refinery furnace, containing a melt below the surface of which air or oxygen is introduced via lances or the like, requires that the depth at which the oxygen is introduced be regulated precisely and be maintained at a substantially constant level. Since the oxygen introduced below the level of the bath oxidizes the carbon contained in the melt to carbon monoxide, which is evolved by the bath and burned above the surface thereof, the exhaust gases of the furnace may be analyzed in order to determine the proper distance of the air of the oxygen lance or nozzle below this level in the bath upon rotation of the furnace. As the furnace rotates, however, the bath level fluctuates periodically in consequence of slight eccentricities of the furnace wall and/or surface irregularities resulting from uneven wear. These unavoidable fluctuations, which change the effective depth of the submersed ox gen blast, superimpose upon the measured output variable, e.g., the exhaust-gas composition, a pattern of rhythmic variations which must be compensated by the control system if the desired stability is to be maintained.

Patent No. 2,977,217, issued March 28, 1961, to Gr-aef et al., points out the relationship between the exhaust-gas composition and the depth of the air-blast nozzle. A further commonly assigned copending application, Ser. No. 825,428, now patent No. 3,043,668 filed July 7, 1959, by Von Bogdandy et al., discloses apparatus for analyzing the waste gases emanating from a furnace of the type referred to and producing an electrical output proportional to the composition of the waste gases analyzed and, consequently, to the depth of immersion of the nozzle.

In the above-mentioned copending application Ser. No. 55,347, the control system disclosed comprises a pair of magnetic tapes adapted to record .a control signal for adjusting the depth of immersion of an oxygen-introducing nozzle and means for compensating for the inherent lag within the control system by increasing the effective length of the tape between a recording and a reading head. It is common knowledge that tape-operated control systems have a, relatively high noise level and are susceptible to maladjustment owing to the nature of the magnetic storage medium.

An object of the present invent-ion, therefore, is to provide an improved control system including mechanical means for recording and reproducing a control parameter, thereby obviating the disadvantages of magnetic recording systems.

It is another object of this invention to provide a mechanism for the continuous recording of a variable suitable for use in analog control installations.

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3,195,111 Patented July 13, 1965 According to a feature of the present invention, the magnetic recording medium disclosed in copending application Ser. No. 55,347 is replaced by a mechanical storage device adapted to be formed with a curve corresponding to the variations of an independent variable with a dependent variable and a reading device mechanically scanning the curve for converting the variations of this independent variable into suitable control action. The storage device advantageously comprises a drum rotatable about an axis and formed with a plurality of axially shifta'ble elongated members extending along generatrices of the drum, the corresponding ends of these members defining the afore-mentioned control curve. The mechanical read-out device may comprise a cam follower bearing upon the ends of the drum members and displaceable in accordance with the contours of the curve formed thereby.

According to a more specific feature of the invention, the drum is formed with a plurality of axially spaced transverse support disks which are perforated around their periphery to receive the elongated members, which may be frictionally received in the peripheral perforations. The disks may include a central disk and a pair of outer disks flanking the central disk. The outer disks which may engage the terminal quarters of the length of the elongated members, have their peripheral apertures lying at a distance from the axis of the drum different from the distance between the axis and the peripheral apertures of the central disk. Thus, the members will be slightly bowed inwardly or outwardly, respectively, at their central region depending upon whether the distance between the peripheral apertures of the central disk is less or greater than the distance between the peripheral apertures of the outer disks and the axis.

The members are, preferably, resilient (e.g. made from spring steel) so that their concave or convex bowing results in frictional engagement with the support disks. To insure that the curve formed by the end faces of the members is substantially continuous, the members have a relatively small width and a large number are provided to form the surface of the drum. The slight rounding of the end faces of the members also facilitates the formation of a smooth curve. A setting device adapted to cam the members into their proper positions upon rotation of the drum is also provided. It should be noted that the frictional engagement of the members by the support disks should be insufficient to prevent displacement of the members by the setting device but sufficient to withstand the pressure of the read-out mechanism.

According to another aspect of the invention, a drum of the aforementioned type is employed in conjunction with a system having a discernible time lag or dead time between the detection of a fluctuation in a measurable output variable and the cause of such fluctuation. Thus, in a rotary refinery furnace wherein the drum is to control the depth of immersion of an air-blast nozzle in response to fluctuations in the composition of furnace exhaust gases, the drum is rotated synchronously with the furnace and a control signal, corresponding to changes in the level of the bath, is fed by the gas-analyzing means to the setting device. The latter shifts the elongated members of the drum axially to form a control curve which is followed by the read-out means and converted into an adjustment of the position of the nozzle upon a successive rotation of the furnace. Advantageously, the setting and read-out means are angularly offset about the axis of the drum by approximately and the drum is coupled with the furnace for rotation at a rate one half that of the latter. The furnace, therefore, makes two revolutions for each revolution of the drums. Since the detection of a change in gas composition does not correspond to a simultaneous alteration in the effective depths of the nozzle owing to the aforementioned time lag or dead time, it is necessary to advance the read-out means relative to the setting means by an amount corresponding to the duration of the lag.

According to another specific feature of the invention, I provide means for relatively angularly displacing the setting and read-out stations about the axis of the drum in order to compensate for the lag. Such means may include a support or carrier for, say, the read-out means which is manually or automatically swingable about the axis of the storage drum by an angle corresponding to the lag. An indicator may be provided for denoting the relative angular positions of the setting and read-out stations and, more particularly, for showing the deviations of the read-out station from its normal position diametrically opposite the setting station when the drum and the furnace are rotated with speeds in the ratio of 1:2.

The above and other objects, features and advantages bevel gears 35. A feedback resistor 12 has a wiper 36 mounted on sleeve 13 and extending through slot 32. This resistor provides a feedback voltage proportional to the actual displacement of sleeve 13 to the amplifier 72 (FIG. 5) of servomotor d and results in an accurate positioning of the cams 6a, 6c in response to an input signal.

The read-out device comprises a pair of similar cams 5a, 50 mounted upon radially extending arms Me, 160 of a sleeve which is axially displaceable relatively to a bar 37 passing through the sleeve. The prismatic configuration of bar 3'7 prevents relative rotation between the latter and sleeve 15 which carries a wiper 38 of a variable resistor 15; whose function will be described subsequently.

' Bar 37 is formed with a pair of axially spaced shoulders of the present invention will become more readily apparent from the following description, reference being made to the acompanying drawing in which:

FIG. 1 is a somewhat diagrammatic perspective view of a storage drum according to the invention;

FIG. 2 is a front-elevational view of a drum showing modified setting and read-out means therefor;

FIG. 3 is a side-elevational view of the apparatus of FIG. 1;

FIG. 4 is a plan view of the apparatus of FIG. 1; and

FIG. 5 is a diagrammatic view of a control system embodying a storage mechanism according to the invention.

In FIGS. 1, 3 and 4 I show a storage drum 1 whose shaft 9 carries three axially spaced transverse disks 7a, 7b, 7c. The central support disk 7b is provided with peripheral apertures tlb which lie along a circle centered upon the axis of shaft 9 and whose radius R is greater than the identical radii R R of the corresponding circles of disks 7a, 7c. The apertures 8a, 80 lie along circles having the radii R and R respectively. A plurality of elongated members 2 form the periphery of the drum and are received in respective bores 811-80 aligned. along generatrices of the generally cylindrical drum. Since, however, the apertures 8b of the central disk 7b are farther from the axis of the drum than the corresponding apertures 811-80 of the outer disks 7a, 70, each of the members 2 is. slightly bowed outwardly at its central portion. These members are, advantageously, resilient and may be made, say, of spring steel so that their bowed configuration results in a frictional engagement of the members with the inner edges of the apertures 8b and with the outer edges of the apertures 8a and 8c. The members are thus restrained from spontaneous movement in axial direction by the frictional forces at these edges. Each member 2 is formed with terminal portions 2a, 2c which contiguously abut corresponding portions of the adjacent members so that their end faces form substantially continuous annular curves 3a, 3c at the upper and lower ends of the drum. The intermediate portion 212 of each member 2 is of reduced cross-section and is received in the bores Sa-Sc.

The shaft 9 of drum 1 is driven synchronously with the rotary furnace, as will be described in greater detail hereinafter, via a bevel-gear transmission 30. The setting means for longitudinally adjusting the members or rods 2 comprises a servomotor 4 and a mechanism designed to convert the rotary output of this servomotor into an axial displacement of a pair of triangular cams 6a, 6c constituting the setting elements. Cams 6a and 6c are carried by respective, radially extending arms 11a, 110 at opposite ends of the drum so that the cams 6a and 6c bear simultaneously upon both end faces of each rod 2 as the drum rotates past the setting station. Arms 11a and 110 are rigid with a threaded sleeve 13 whose rotation is prevented by an axially extending guide slot 32 in a wall 33 of the support structure for drum 1. A screw 34 threadedly engages sleeve 13 and is journaled in the support structure for rotation by the servomotor 4 via 38a, sac against which a pair of compression springs 3%, 39s are seated. Springs 39a, 3% bear against a ring 4011 which surrounds the shank 38b of bar 37. Ring 49b is rigid with sleeve 15 so that the springs 3%, 390 tend to maintain this sleeve in an intermediate position and to return it to this position upon axial displacement of the sleeve by the curves 3a, via followers 5a, 50. It should be noted that springs 39a and 390 apply less force to the rods 2 than is required to overcome the frictional forces acting thereon and thus avoid dislodging the rods once they have been set by cams on and 60. Bar 37 is carried by a radially extending arm 41 journaled on shaft 9 for rotation about the axis of the latter. Thus, arm 41, bar 37 and the read-out follower elements 5a, 5c may be swung angularly about the axis of drum 1 by a distance sutlicient to compensate for the duration of the time lag.

While the angular displacement of arm 41 can be effected by means of a servomotor such as a mechanism employed to deflect the tape in the Bogdandy et al. application Ser. No. 55,347, I prefer to position it manually after experimental determination of the duration of the time lag or dead time to compensate for the latter. As locking means I provide a knurled screw 42 Which is threadedly received in a pointer 43 secured to a stud 44 extending axially from boss 45 of arm 41. The pointer 43 sweeps a scale 46 of indicator means 17 denoting the relative positions of the setting and read-out means. Scale 46 is held stationary by an arm 47, which is provided with a boss 48 rotatably receiving a stud 44 rigid with the support structure.

In FIG. 2, there is shown a modified arrangement of a control device wherein the drum 1' is provided with support disks 7a, 7b and 7c. The peripheral apertures 8b are located along a circle whose radius is somewhat less than the radii of the corresponding circles along which the apertures 8a and 8c of disks 7a and 7c lie. Thus the rods 2', which are shown schematically in FIG. 2 and actually have a configuration similar to that shown in FIG. 1, are slightly concave outwardly so that they frictionally bear against the outer edges of apertures 8b and the inner edges of apertures 8a and In this embodiment, however, the sensing cams 5a, 5a and the setting cams 6a, 60' are rounded off at their surfaces in contact with the curves 3a, 30' formed by rods 2'. The arms 15a, 16c carrying the sensing cams 5a, 50' are rigid with a rack 15' guided between pairs of rollers 49', 50 journaled in a support plate 51'. A pinion 52 engages the rack 15' for rotation by the latter to drive an electromechanical transducer such as servomotor Ztl and operate a control element. Plate 51 is carried by arms did, 410' for swinging movement about the shaft 9' of drum 1. Arm 41a is provided with indicating means 17 similar to the indicator 17 previously described.

The setting cams 6a, 6c are mounted upon arms Illa, Illc' rigid with a rack 10 guided between the rollers 53, 54 journaled in a stationary plate 55. A servomotor 4' rotates a worm 56' to drive a pinion 57' which, in turn, displaces the rack 10'. The feedback signal is, in this instance, derived from a servomotor 14' which is driven by pinion 58 from rack 1d. Servomotor 21 drives shaft 9' via the bevel gears 36.

FIG. 5 illustrates a control system embodying a mechanical storage device of the character previously described. For convenience, prime numerals have been employed in FIG. 2 and double-prime numerals in FIG. 5 to indicate elements equivalent to those designated with identical but unprimed reference characters in FIG. 1. In FIG. 5 I show a rotary furnace 60 containing a bath 6, of a metal (e.g. iron) to be refined. Through one end of furnace 60, which is rotatable on rollers 62, 63 about a substantially horizontal axis, an oxygen lance 64 is introduced below the surface of the bath. The lance 64 is fulcrumed at 65 to a support 66 and is provided with a nut 67 threadedly engaged by a lead screw 68. The latter is driven via bevel gears 69 by a servomotor 20".

At the output end of furnace 69 a duct 70 is provided to carry away the exhaust gases. The carbon-monoxide content of these gases is analyzed by a device 71 of the type disclosed in the above-mentioned Bogdandy et al. ap plication Ser. No. 825,428 filed July 7, 1959. The voltage output of the gas analyzer 71 is fed to a servo-amplifier 72 which also receives a voltage indicative of the position of the setting elements 6a, 60'. These elements are, in the device shown in FIG. 5, rollers mounted upon arms 11a", 11c" extending from sleeve 13" of a setting device such as that shown in FIG. 1. The reference voltage is derived from a potentiometer 12 and a battery 73. Amplifier 72 controls a servomotor 4" which reversably drives a screw 34 of the setting device whenever the input to amplifier 72 from the analyzer 71 differs from that derived from the feedback potentiometer 12". Consequently, setting elements 6a" and 6c" are always positioned in response to the gas composition and, therefore, the effective depth of immersion of the lance 64.

The drum 1 is rotated by its follower servo 21 at half the speed of rotation of furnace 64). The latter is driven by a motor 76, constituting a servo transmitter, whose pinion 75 meshes with the ring gear 74 of furnace 69. Motor 76 is fed with alternating current in the usual manner from a source 77. As the furnace 66 rotates, the effective level of the bath 61 fluctuates periodically, thereby alterning the depth of immersion of the lance 64. Changes in the carbon-monoxide concentration of the gas resulting from variations in the depth of the immersion of lance 64 are sensed by the analyzer 71 with a lag proportional to the volume of the furnace. The previously recorded curve 3" of the storage device 1", however, now displaces the follower rollers 5a", 50 of the read-out means and shifts their support body 15" so that the wiper 38 of the associated potentiometer 18" produces a con trol-voltage output representative of the required correction of the position of lance 64. Potentiometer 18" bridges a battery 73 and feeds its control voltage to a servo-amplifier 79 which is also supplied with an input from a feedback potentiometer 8t) bridged across another battery 81. The slider 82 of potentiometer St is connected to nut 67 and thus indicates the actual position of lance 64. Consequently, an imbalance between the two inputs is established whenever the support body 15" is shifted by the storage drum 1" in a manner tending to adjust the position of the lance. In the usual manner, amplifier 79 produces an error signal which drives the servornotor 20 to operate screw 68 and reposition the lance 64 at the point at which the two inputs are again in balance. Advantageously, the swingable arm 41" carrying the readout means has previously been locked relatively to the setting device so as to compensate for the time lag.

The invention as described and illustrated is believed to admit of many modifications and variations within the ability of persons skilled in the art; all such variations and modifications are deemed included within the spirit and scope of the invention recited in the appended claims.

I claim:

1. A mechanism for analog recording of a variable of a cyclical progress, comprising support means displaceable about an axis; a plurality of elongated members shiftably mounted on said support means for displacement in generally axial direction and extending along respective generatrices of a surface surrounding said axis, said elongated members being formed with corresponding faces defining an annular curve characteristic of said variable; axially shiftable setting means cammingly engageable with said members for axially displacing them in accordance with fluctuations in said variable upon displacement of said members on said support means along a closed path; and read-out means along said path cammingly displaceable by said faces upon said displacement of the said support means; servo means operatively connected with said setting means for shifting same; position-sensing means responsive to axial displacement of said setting means; and circuit means forming a feedback path between said position-sensing means and said servo means.

2. A mechanism for analog recording of a variable of a cyclical process, comprising support means rotatable about an axis; a plurality of substantially contiguous elongated members shiftably mounted on said support means for displacement in generally axial direction and extending along respective generatrices of a surface of revolution centered on said axis, said elongated members being formed with corresponding faces defining an annular curve characteristic of said variable; axially shiftable setting means cammingly engageable with said members for axial- 1y displacing them in accordance with fluctuations in said variable upon displacement of said members on said support means along a closed path; and read-out means along said path cammingly displaceable by said faces upon said displacement of said support means; at least one of said setting and read-out means being provided with a carrier swingable about said axis relatively to the other for adjusting the mutual angular spacing between said setting and read-out means.

3. A mechanism according to claim 2 wherein said support means comprises at least three axially spaced disks including a central disk and a pair of outer disks flanking said central disk, each of said disks being provided with peripheral apertures for receiving said members, the peripheral apertures of said central disk being located at distances from said axis different from the distances between the peripheral apertures of said outer disks and said axis whereby each of said members is frictionally entrained with apertures of said disks lying along a respective generatrix of said surface.

4. A mechanism according to claim 3 wherein the peripheral apertures of each of said disks lies along respective circles centered on said axis, the radius of the circle of said central disk being different from the radii of the circles of said outer disks.

5. A mechanism according to claim 2 wherein said elongated members are of identical length and are each formed with a pair of end faces lying along parallel annular curves at opposite extremities of said surface, said setting means comprising a pair of setting elements axially spaced by a distance equal substantially to the length of said members and engageable with the opposite end faces thereof.

6. A mechanism according to claim 5 wherein said setting means comprises an axially shiftable body carrying said setting elements and servo means operatively connected with said body for shifting same.

7. A mechanism according to claim 6 wherein said setting means further comprises position-sensing means responsive to axial displacement of said body, and circuit means forming a feedback path between said positionsensing means and said servo means.

8. A mechanism according to claim 5 wherein said readout means comprises a pair of follower elements axially spaced by a distance equal to the length of said members and engageable with respective end faces thereof.

9. A mechanism according to claim 8 wherein said readout means further comprises an axially displaceable body 7 carrying said follower elements and electromechanical transducer means coupled With said body for providing a control signal upon displacement thereof in accordance with the contours of said curves.

19. A mechanism accordingto claim 2 wherein said setting and read-out means are spaced angularly apart by approximately 180, further comprising drive means for said support synchronized With said cyclical process for rotating said support means one revolution for each two cycles of the process.

It. A mechanism according to claim 2 further comprising indicator means coupled to said carrier for denoting the relative angular positions of said setting and read-out means.

12. A mechanism according to claim 2, further comprising locking means for securing said carrier against displacement in a selected angular position about said axis.

13. In a control system for a rotating reaction vessel having output means adapted to produce :an output signal representative of the progress of a reaction in said vessel and input means adjustable for changing an operating parameter to influence the reaction with an inherent time lag between the adjustment of said input means and a resulting change in said output signal, the improvement which comprises a mechanical storage device for analog recording of said output signal, said storage device comprising support means rotatable about an axis, and a plurality of elongated members'shif-tably mounted on said support means for displaceemnt in generally axial direction and extending along'respe ctive generatrices of a surface of revolution centered on said axis, said elongated members being formed with corresponding faces defining an annular curve characteristic of said variable; axially shiftable setting means cammingly engageable with said members for axially displacement them in accordance with fluctuations in said variable upon displacement of said members on said support means along a closed path; readout means along said path cammingly displaceable by said faces upon said displacement of said support means, and circuit means connecting said read-out means and said input means for adjusting the latter in accordance With the contours of said curve, said read-out means comprising a carrier swingable about said axis relatively to said setting means for conpensating for said time lag.

References Cited by the Examiner UNITED STATES PATENTS 2,852,727 9/58 Barnett 3l8162 3,131,379 4/64 Holt 340-473 IRVING L. SRAGOW, Primary Examiner.

Claims (1)

1. 2. A MECHANISM FOR ANALOG RECORDING OF A VARIABLE OF A CYCLICAL PROCESS, COMPRISING SUPPORT MEANS ROTATABLE ABOUT AN AXIS; A PLURALITY OF SUBSTANTIALLY CONTIGUOUS ELONGATED MEMBERS SHIFTABLY MOUNTED ON SAID SUPPORT MEANS FOR DISPLACEMENT IN GENERALLY AXIAL DIRECTION AND EXTENDING ALONG RESPECTIVE GENERATRICES OF A SURFACE OF REVOLUTION CENTERED ON SAID AXIS, SAID ELONGATED MEMBERS BEING FORMED WITH CORRESPONDING FACES DEFINING AN ANNULAR CURVE CHARCTERISTIC OF SAID VARIABLE; AXIALLY SHIFTABLE SETTING MEANS CAMMINGLY ENGAGEABLE WITH SAID MEMBERS FOR AXIALLY DISPLACING THEM IN ACCORDANCE WITH FLUCTUATIONS IN SAID VARIABLE UPON DISPLACEMENT OF SAID MEMBERS ON SAID SUPPORT MEANS ALONG A CLOSED PATH; AND READ-OUT MEANS ALONG SAID PATH CAMMINGLY DISPLACEABLE BY SAID FACES UPON SAID DISPLACEMENT OF SAID SUPPORT MEANS; AT LEAST ONE OF SAID SETTING AND READ-OUT MEANS BEING PROVIDED WITH A CARRIER SWINGABLE ABOUT SAID AXIS RELATIVELY TO THE OTHER FOR ADJUSTING THE MUTUAL ANGULAR SPACING BETWEEN SAID SETTING AND READ-OUT MEANS.

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