US2460199A - Measurement or variation of physical states of materials - Google Patents

Description

Jano 25p 1949- M. K. TAYLQR ET AL. 460B? MEASUREMENT OR VARIATION OF PHYSICAL STATES OF MATERIALS 3 Sheeis-Sheei; l

Filed Oct. 2l, 1946 Jan. 25, 1949. M. K. TAYLOR ET Ax. 2,46099 MEASUREMENT OR VARIATION OF PHYSICAL STATES OF MATERIALS 3 Sheets-Sheet 2 Filed 00T.. 2l, 1946 Jan. 25, 1949.

M. K. TAYLOR ETAL 2,460,199 MEASUREMENT OR VARIATION OF PHYSICAL STATES OF MATERIALS Filed oct. 21, 194e 3 Sheets-Sheet 3 VOLTS VOLTS Patented Jan. 25, 1949 MEASUREMENT on VARIATION lor PHYSICAL STATES OF MATERIALS Maurice :Kenyon Taylor, Belmont, Scotland, and

Alfred DouglasA Knowle assignors to Ferranti L land, aiBritjish company Applic'ationOctober 21, 1946, Serial No.

s, Chadderton, England, imited, Hollinwood, Eng- In `Great Britain October 1945 2 Claims. l

This invention relates to the variation of the physical state of materials such as the dampness ofV cloth, Vand in particular to apparatus for achieving this Apurpose-by utilising the effect of variation of the physical state on a condenser of which the material forms all or part of the dielectric.- p

The main object of* thepresent invention is to provide means for varyingthe speed of travel of a continuous or longpiece ofthe material through a. treatment zone. in Vwhich the physical characteristic to be 'controlled'.is varied, the variation in speed being dependent upon variation of the physical state from a required standard. For example cloth maybe passed through a drying oven to control its humidity. If the cloth emerg- .ing fromthe` oven is too'damp the speed of the material through the' oven will be decreased and vice versa. ...According .to the present invention a method ofvarying the physical state of a material comprises moving the material through an oven or other treatment zone, deriving a voltage which is proportional to thedampness or other physical stateof the material, said voltage being derived onlyl 'at predetermined regular distances along the material, and positively or negatively accelerating the motion of said material for periods of acceleration proportional to the voltage so derived.

Thus in accordance with the invention the material is tested only at regularly spaced intervals and lthe speed of movement of the material through the treatment zone is varied at similar intervals if the physical state varies from the required value the variation of speed being in the required corrective direction and to a degree proportional tothe degree of variation from the standard. The rate of variation of the speed may be constant, and the duration of this variation being proportional over the control range to the degree of variation from the standard.

An apparatus forcarrying out the invention may comprise means for moving the material through an oven or 'other treatment zone, means for positively and negatively accelerating the motion of said'materlal,vo1tagederiving means for deriving a1 voltage which is proportional to the dampness or other physical state of the material, means for rendering the voltage-deriving distances along the material,` andy relay means @WP-11rd by the. derived. veltase so as *w accelil-Siigj @@1031 lesitivelr. .011 ,negatively 'for periods of acceleration proportional to said voltage.

The derivation of periods of acceleration from and proportional to the degree of said voltage may condenser whichr is periodically discharged by means' of a gas-dis charge tube, which completes a relay circuit. Two such valve-and-tube circuits `maylbe provided ied with voltage of/opposite polarity and serving to initiate and stop the positive or negative accelerations.

The movement of the 'material through the oven may be effected byan electric motor"the speed of which can be altered by altering the position of its brushes by means of a pilot motor controlled by the relay.

For rendering the current-deriving means operative only at predetermined'intervals a 'commutator device may be provided. in the hightension lead to the valve whereby the 'high-'tem intervals, the speed of the commutator.l being controlled so that the said intervals correspond with similar lengths oimaterial irrespective of the speed of travel of the material.

A constructional form of the invention will now be described by way of example wtih reference to the Yaccompanying diagrammaticdrawings in which:

Figure l shows the electrical layout of an apparatus for deriving appropriate voltages;

Figure 2 shows the electrical layout of additional apparatus to be used inconjunctionwith the apparatus shownin Figure l,.for controlling the speed of cloth through an oven in accordance with the present invention; y

Figures 3 and 4. are graphs to be referredto; and

Figure 5 shows a detail to be described.V e

An oscillator triode Ill has its grid connected by a suitable gridlead Il to earth, this grid-lead having a by-pass condenser` l2 connected across it. The anode is connected to one plate of a iixed condenser i3, between the other plate of which and earth is a variable tuning condenser I4. This condenser is motor operated and the condenser an-rl motor will be hereinafter more fully described. The anode is .also connected vto a position between two inductance coils l?, i3, `which are in series and the second of which is connected to"'oneV plate of la xed condenser lathe. other plate ot which isv connected to. oneterminalof a 3 switth 28 the other terminal of which is earthed. The switch 2t is operated by a relay controlled by a commutator to be described later. The other coil is connected to one plate of a condenser 2l the other plate of which is earthed, and it is also connected to a high-tension supply and by a choke coil 22 to the anode of a pentode amplifier valve 2d the control grid of which is connected by a fixedY condenser 25 to the triode cathode, the latter also being connected toearth through Va suitable choke 25 and to one plate of another condenser 21 the other plate of which is connected to the triode anode. rlhe cathode and control grid of the pentode are also earthed through suitable resistances 2%, Sii respectively. The anode of the pentode` is connected to one plate of a condenser 3i the other plate of which taneously moves over to contact 55.

is connected to earth through two inductance coils 32, 33, in series, which Vrare coupled respectively with inductance coils/,34, 3,5 respectively in two tuned circuits. The standard circuit contains a variable resistance 3% and variable condenser 31 while the measuring circuit contains the plates .t3V between which the material is .asscd, both circuits being earthed by lead 13S. rThe inductance coils 32, 33, are connected to the cathode of a diode detector valve d'2 the anode of which is connected to the control grid of a second pentode valve G3 the cathode of which is earthed and between this anode connection and earth are a condenser iid and a resistance l5 in parallel. The 'second pentode anode is fed with hightension current through a resistance 48 in parallel with a condenser t9, and is connected by a condenser t tothe control grid of a third pentode valve 5i, this grid being also earthed through a resistance 52; the cathode of valve 5i is earthed through a resistance. The lanode of the third pentode is connected through the primary coil 53 Y, of a transformer to the high-tension supply, a

shunt resistance 513 being provided across this coil.'V The Vsecondary 55 of this transformer has contact pointsj'i', 58, engaged alternately by a movable switch member 59 which is operated by a relay in synchronism with the switch 2i?. The mid-point of this secondary is earthed by a lead Gli so that, as will be more fully described hereinafter, the opposite ends, 5l, 62, of the transformer are of opposite polarity. The switch member 59 is `connected toa condenser G which is earthed and in parallel with this condenser is a smoothing resistance 55 and condenser 58. A lead 51, between the smoothing resistance' and condenser, is taken to the device for controlling the physical state of the material under test which is described'below. The other grids of the pent-ode valves are provided with any normal conr. ons customary to their use as amplifying vr'fes. Leads 63, S9, are connected to hightension supply-positive and negative respectively.

The construction and operation oi the parts M, 2G, and 59 is shown more fully in Figure 5. The condenser ill comprises a series of xed plates 1l which are quadrantal in shape and a series of movable plates 12 which are earthed by a slip ring (not shown) and have a similar shape to the nxed plates. VThe movable plates are fitted on to a rotatable spindle 13 and are symmetrically arranged so as to form two diametrically opposite sets. Rotation of the spindle is eectedby a small motor 11i.

The spindle 13 carries a commutator T55 which is composed of alternate quadrants of conducting and insulating material. The Vcornmutator is engaged by two brushes 4 8U, 8l, the former of which is connected to a relay 15, and the latter of which is earthed. Relay 1S controls switches 25 and 5S; when the relay is not energised switch 2i) is open and switch member 5S makes contact with contact 51; when the relay becomes energised switch 2t closes and switch member 59 simul- By this arrangement one set of plates 12 will move through approximately degrees whilst the sec= ond inductance coil I8 and condenser i9 are included inthe oscillator circuit thereby sweeping a frequency band which includes the resonai` frequency of the standard circuit and a pulse oi' negative polarity is taken from the contact 55 end of the transformer secondary 55; whereupon the commutator causes the relay 16 to open switch 2) and reverse switch 59 so that the second inductance coil is no longer included in the circuit and during the next 90 degreesoi revolution of the condenser plates a different frequency band will consequently be swept which includes the resonant frequency of the measuring circuit, and Va pulse of positive polarity is taken from 'the con# tact 51 end of the transformer secondary.` During the next degrees of movement ofthe condenser plates the effect is repeated with the other set of movable condenser plates. It is arranged that the tuning -condenser is at a maximum or minimum value when the second inductance coil is switched in or out of the oscillator circuit so that each frequency band is covered in one direction. Y

In the arrangement described above voltages are derived from both the standard and measuring circuits which are amplitude modulated by the loscillations supplied by the oscillator. The amplitude in each tuned circuit is a' maximum Y when the oscillator frequency coincides with the resonant frequency of rthe tuned circuit. These voltagesare applied to a diode rectifier to effect demodulation. The resultant signal has a pulsatory wave form which is amplied by the second pentode after which the pulses from one circuit are made negative and the pulses fromthe other circuit are made positive by means -oi the changeover switch 59 with a View to adding them in order to obtain the arithmetical difference. For this purpose the pulses are applied to the grid of the pentode valve in the anode lead or" whichis the transformer 53, 55 thesecondary coil of which as already described has its centre point vconnected to earth so that pulsesof opposite polarity derived from the two tuned circuits are developed across that` half of the secondary brought into action by switch 59. The condenser accordingly receives alternate positive and Ynegative charges.v The pulses ar-e smoothed by means oi the condenser 66 and resistance G5, thereby giving a D. C. level of voltage corresponding to thefdifference in the magnitude of the pulses; v

if the iinal output difference isl negativerthe Q value of the measuring circuit is too snlall and the material is too wet. Iii the voltagediiference is positive the Q value of the measuring circuit is too large and the material is too dry. If the voltage is Zero the two Q values lare the same and the material has therequirecl moisture content.V l Y d Y Y The apparatus so vfar described comprises the subject of co-pending British patent application No. 28,177 ofV i945 in which itis more fully described. f .Y n u Y For the purposeof .thef present invention the additional apparatus shown in Figure 2 is provided in which. 55 the. sametransformer .Secondary coil as is shown in Figure l, andthe switch 59, contacts 513,158, condensenG-fl, `resistance-65,. condenser 66,- and output lead 61, `also represent the same parts as are indicated by the same numerals in Figure l. Y e

The voltage across condenser 66 is proportional to the deviationin` wetness ofv the4 material .from therstandard. lfgthe `material is too dry this voltage is positive whileif lth s yoltageis negative the material is too wet. o Y i f y Anothervoltage is obtained by a lead 80 (taking the place of the lead 60) from the centre tapping point of the coil 55,;this voitagebeing smoothed byrcondenser 8|. andresistance82. vAcondenser 83 is also provided corresponding.- to the condenser 68. [The nvoltagesacross condensers 66 and 03 are therefore equal but of opposite polarity. Thus if `the original voltage across condenser 69 is illustrated by the graph Figure 3, the voltage across condenser 83 will be as illustrated by Figure 4. Y

These voltages are applied respectively to separate similar circuits. The ilrst of these circuits includes a pentode valve 86 to the control grid of which the lead 61 is connectedf The cathode of the valve is connected by way of a resistance 90 to the earthed negative pole of a high-tension supply. In the lanode leadof the pentode valve are a condenser 81 anda resistance 88 in parallel; the anode side of condenser 81 is connected to the cathode of a gas-discharge'tube 9|; the other side oi the condenserv is connected to the positive pole of the high-tension supply and` to one end of an energising coil A92 the other end-'of which is connected to the travelling contact oi a single-pole double-throw switch 93,V OneXed contact 93A of this switch is connected' tothe 'anode of the gas-discharge tube 9| and the other iixed contact 93B is connected to earth through another energising coil 94 the purpose of which will be described later. The second of theafo'resaid two circuits comprises similarly connected valve 96, condenser 91, resistances 98 and |00, gas-discharge tube coil |02, switchm |03, and coil |04.` The coil 92 actuates the switch 93.` 'When coil 92 is not energisedthe travelling contact rests on contact 93A; when energised the travelling contact moves to contact 93B and is there held on till the circuit external to the relay is broken, as will be described later. Coil |02 actuates the switch |03 in like manner to connect |02 alternatively to the anode of the gas-discharge tube |0| in the other circuit by way of :fixed contact |03A or to coil |04 by way of xed contact 503B.

The current through each of the pentode valves varies according to the potential applied to the grid. The condenser in the anode lead is thus charged at a rate which depends on the current and consequently on the potential applied to the grid, this potential being proportional over the working range of the apparatus to the degree of variation of the dampness of the cloth from the standard. If the voltage applied to the grid is positive the condenser charges up quickly but if this voltage is negative a comparatively long period is required to charge the condenser. The condenser charges up until the plates reach the potential of the striking voltage of the gas-discharge tube which accordingly becomes conducting thereby completing a circuit through 92, the tube 9|, and switch 93 (by contact 93A). Thereupon, coil 92 being energised, switch 93 operates and completes a circuit from the` positive hightension supply through 92, 93 (by contact 93B), and 94 to the negative high-tension pole, thereby energising coil 94. Hence the time taken to complete the latter circuit depends on the timeat which the gas tube flashes. If a large positive voltage (indicating too dry material) is applied to the grid of the pentode 86 the coil 94 is energised almost immediately; if a small positive voltage is applied to the grid, switch 93 will not move as soon; and if a negative voltage, indicating too wet material) is applied to the grid, switch 93 will not move until after a comparatively long period. The other circuit behaves similarly except that/since the current input to its pentode valve 96 is of opposite phase, quick energisation of coil |04 indicates too wet material and slow energisation too dry material.

' The coils 94, |04, actuate two'relay switches |06, |01, respectively. Switch |06 has four contact points, Hi, H2, H3, H4, and switch |01 also has four contact points H5, H9, H1, H8, Points H2, H3, H5, H8, are all connected together electrically in a permanent manner. Contacts H4 and H1 are also connected together and to one lead from the supply for the windings of a split rleld pilot motor |20. Contacts and I6 are respectively connected to the ends of the two iield windings oi the motor, the common point of the windings being connected to the other supply lead. The pilot motor drives a toothed member |2| which carries the brushes of the main motor !4 which in turn drives a roller |23 that conveys the material |24 through an oven |25 that contains thetesting condenser 38 offFigure l. The contact Hl is connected to that eld winding of the pilot motor which effects an increase in the speed of the main'motor while contact |6 is connected to that winding which eiects a decrease in the speed of the main motor. The contacts l I3. H4, and l1, H8, vare connected by the movable contacts oi relays 94 and 04 when these relays are not energised and then there is no current to the pilot motor so that the main motor speed is unaltered, When relay 94 is energised its movable contact connects contacts III, H2, instead of contacts H3, H4, and 'when relay |04 is energised its movable contact connects contacts H5, H6, instead of contacts H1, H8.

If for example the cloth is very dry a large positive voltage is applied to the grid of the pentode associated with relay 94 so that the movable contact of switch |06 will change from contacts H3, H4, to contacts H|, H2 almost immediately. The iield winding current of the pilot motor then has a path through contacts H1, |8, and contacts |H, H2, and operates the pilot motor to accelerate the main motor so that the cloth passes more quickly through the oven and does not get so dry. At the same time a large negative voltage is applied to the grid of the pentode 96 and the movable contact of switch |01 therefore changes at a later time from contacts H1, H8, to contacts H5, H6. The contacts H3, H4, and H1, H8, are now both open so that current controlling the relay has no outlet path and the motor therefore stays at its altered speed. The motor is therefore positively or negatively accelerated in the period between the operation of the switches |06 and |01, andthis period is approximately proportional to the degree of variation of the dampness from the standard.

The speed of the motor is not continuously varied but variation is effected at intervals corresponding to intervals of distance along the cloth Yat which periodic tests are made. 'Ifhus upon making a test on one part of the clothl adjacent to the outlet end of the oven i. e., if the condenser 3S is located at the outlet end of the' oven, the speed of the next length of cloth (equal to the length of the oven) is altered according to the degree ofdeviation of that part from the required standard of humidity. This is effected as follows. In the high-tension lead |28 to thev pentode anodes is a disc 29 of insulating material which is rotated by geared connection to the main motor so that the disc makes one revolution in the period during which one position on the cloth travels the length of the oven. As the speed of the motor alters so does the speed of thisdisc. At one position on the circumference Y of this disc is a small piece |30 of conducting ma terial. As the disc rotates high-tensionV current is applied to the valves through this conducting piece once for a short period during each revolu-` tion of the disc. The valves are therefore only effective during these short periods and consequently only at 'these intervals is the test made on a small part of the cloth and the speed of the motor altered accordingly. This disconnection of the high-tension supply at the end of each short period de-energises the coils of relays 92 and lH12 thus causing them to restore, i. e. the travelling contacts to Vmove from fixed contacts 93B and 103B to xed contacts 93A and 103A respectively.

The main motor 14 also drives the switch 20, condenser I4, and switch 59, so that the operation of these partsk is suitably related to theV operation ofthe disc |29.

Should it he desired to eiect control more frequently than the llength of the oven allows, the condenser plates between which the cloth passes for test'purposes are placed nearer to the point of entry of the cloth into the oven. By this arrangement allowance is made for drying Subsc-'- quent to the measuring position. The length of cloth over which correction is made at corresponding intervals is that between the start of the oven and the measuring position.

AWe claim:

1. An apparatus for controlling the movement of material in accordanceV with variations inthe 8 physical state thereof comprising means for moving the material relative to a treatment zone, means for positively and negatively accelerating the motion of said material, voltage deriving 1 means for deriving two control voltages one of which is positive, and the other of which is negative according to the direction of deviation from a standard and each of which is proportional to the dampness or other physical state of the mai6" terial, means for rendering the voltage deriving means operative only at predetermined regular distances along the material, a pair of condensers adapted to be charged at-rates dependent on the polarities and potentials of said control voltages 15' respectively, means for discharging the condensers when predetermined potentials are reached, and relay means operated by the discharging current and controlling the operation of said accelerating means lso as to accelerate said motion positively Aandrnegatively according to which of the condensers discharges first, said relay means being also operated to stop the acceleration when the other condenser discharges, whereby the period of positive or negative acceleration is pro- 2'5 portional to the period between discharging of the two condensers.

l 2. An apparatus as claimed in claim 1 wherein said control voltages are respectively applied to the grids of two valves the current through 30 which varies according to said voltage, and the anodes ofthe valves are connected respectively to the condensers which are periodically discharged by means of gas-discharge tubes which complete relay circuits.

35 l YMAURICE KENYON TAYLOR.

ALFRED DOUGLAS KNOWLES.

REFERENCES CITED The following references are of record in the o file of this patent:

UNITED sTATEs PATENTS Lnja et ai sept. 19, 1944

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