US2251535A - Control instrument - Google Patents

Description

-Aug. 5, 1941. R. ULLMAN 2,251,535

CONTROL INSTRUMENT Filed June 14, 1938 HHHHH INVEN TOR. {)Y ULLMAN BYHW A TTORNEY Patented Aug. 5, 1941 I I CONTROL INSTRUMENT Roy Ullman, ltodyn, Pat, aasignor to The Brown Instrument Company, Philadelphia, Pa, a corporation of Pennsylvania Application June 14,1938, Serial No.213,620

' comma, (01. 236-74) The general object of the present invention is to provide improvements in control instruments of the type including a measuring element deflecting in accordance with a measurable control quantity, and a relay mechanism or power device through which said measuring element affects adjustments of a control device which are not practically obtainable through direct connection of the measuring element and control device. More specifically, the object of my invention is to provide an instrument of the type mentioned with mechanical relay provisions of novel construction to establish a relation between the movements of the deflecting element and control device, which is desirable in respect to both the magnitude and timing of said variations.

My improved instrument is adapted to a wide range of uses, inasmuch as its deflecting element may be responsive to, and by its movements be, a measure of temperature or pressure, or other physical condition, which by changes gives rise to variations in a measurable force resulting in control actions selectively dependent upon such variations.

In a preferred form of my invention, a variation in the condition being measured determines the setting of a directional switch in the relay. Another switch in series with the directional switch regulates the amount of energization of a motor in the control device. The second switch may be closed for either a predetermined time each cycle or for a variable time depending upon the variation of the measured condition from a desired value.

a The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, however, its advantages and specific objects obtained with its use, reference should be had to the accompanying drawing and descriptive matter in which I have illustrated and described a preferred embodiment of the invention.

Fig. 1 is a view including an elevation of the,

relay, and including a diagrammatic representation of furnace control provisions cooperating with the relay to maintain predetermined furnace conditions;

Fig. 2 is a view of a modified relay; and

Fig. 3 is a view showing various of the parts of the modification of Fig. 2 disassembled.

In the embodiment of the invention shown in Fig. 1, my improved control instrument comprises mechanism which may be located in an ordinary instrument casing. The instrument is employed to adjust a fluid supply valve l of a furnace or heater 2 as required to maintain a predetermined furnace temperature to which a device 3 is responsive. As shown, the device I is the bulb of a fluid pressure thermometer, the pressure of which istransmitted by a tube 4 to the stationary end of a Bourdon tube 5 that adlusts the position of a contact member 6 pivoted at I. As the temperature in the furnace varies, the tube 5 expands or contracts to raise or lower the contact member 6 which forms part of a proportioning system to be later described.

I A reversible motor 8 comprising two reversely wound fields l and i is connected to the valve l to open or close it, depending upon the variations in temperature of the furnace 2. Both of the motor fiels 8 and H) are connected by a lead H to one side L' of an alternating current supply system of customary commercial voltage for lighting and power purposes. The other side of the line L goes through conductor l2 to a timing mercury switch I3 and from there through line H to one contact of each end of direction controlling mercury switch Hi. The other contact of the left end of switch l goes through conductor 16 to field .9 while the second contact of the right end of switch l5 goes through conductor H to field III.

The timing switch I3 is mounted for tilting movement on a combined bracket therefor and lever it that is pivoted at I! and has a normal gravitational bias in a counterclockwise direction. The other end of the lever l8 has a roller 20 thereon that bears against a constantly rotating cam 2| which serves to control the tilt-. ing movement of the lever is and therefore the opening and closing of the switch lit. The cam 2| is made up of two concentric parts 21a and 2), one of which is fastened to, and the other of which is rotatable on, a shaft 22. The part 2lb, which is rotatable on shaft 22, has a series of holes in it, through any one of which a screw 23 may be inserted and screwed into a hole in part 2la fastened to the shaft. By this means the percentage of high and low portion of the cam may be varied. The shaft 22 is driven through gearing 24 from any suitable constant speed motor (not shown).

The direction controlling switch i5 is mounted for tilting movement on an abutment member 25 that is pivoted at 28 and is biased in a clockwise direction by a spring 21. This abutment member has an arm 28 on the lower end of which is a roller 2! bearing on a cam 30 fixed to shaft 22 in a definite angular relation to part 2| a of cam 2|. The left end of abutment member has adjustably attached to it another abutment member 3|. As the cam rotates with shaft 22, it periodically moves the abutment member 25 and its attached switch |5 in a counter-clockwise direction and then permits them to move clockwise under the bias of spring 21 to a position depending upon the then value of the condition being measured.

The point at which the clockwise movement of member 25 is terminated depends upon the position of an arm 34 of a relay 35 which is responsive to changes in the value of the condition. This arm can engage either edge 33 or edge 32 of the abutment members 25 and 3|, or can miss them entirely, and thus cause the contacts at one end or the other of switch |5 or neither set of contacts to be closed. The relay 35 comprises a tilting'member 36 that is fastened to arm 34 and is pivoted around a pin 31. Member 36 has formed on each of its ends cores 38 and 39 that are arranged in inductive relation with coils 40 and 4| respectively. A spring 42 is fastened to the frame of the relay 35 and the member 36 to lightly normally bias this member and arm 34 into their mid-position.

Angular adjustment of contact member 6 by the Bourdon tube 5 controls the adjustment of the heater supply valve and gives the latter adjustment movements in a direction corresponding to the adjustment of contact member 6. The adjusting means forms part of the control instrument and comprises an electrical resistance 43 so disposed that as the contact 6 moves through its range of oscillation, it will engage the resistance 43 at different points along its length. Conductors 44 and 45 are connected to the ends of resistance 43, and a conductor 46 is connected at'lto the end of contact member 6. The conductors 44 and 45 are connected to the ends of a resistance 41 which is engaged by a contact member 48 that is movable along the resistance 41 in a manner similar to the movement of member 6 along resistance 43. The resistances 43 and, 41, conductors 44 and 45, and contact members 6 and 48 form parts of a Wheatstone bridge arrangement which is energized by a transformer 49, the terminals of the primary windings of that transformer being connected by conductors 50 and 5| to conductors 44 and 45 respectively. The terminals of the secondary winding of transformer 49 are connected to the A. C. supply L and L The relay 35 forms part of the proportioning means and is connected to the Wheatstone bridge arrangement in the following manner. The con ductor 46, extending from junction 1, forms a common lead for each coil 40 and 4| while coil 40 is connected by conductor 52 to conductor 5| and conductor 45, and coil 4| is connected by conductor 53 to conductor 50 and conductor 44.

In any condition of stable operation, the currents flowing through relay coils 40 and 4| will be equal, and the armatures 38 and 39, member 35, and arm 34 will be in their neutral position so that upon an upward movement of abutment 25, arm 34 will engage edge 32. Any deflection of contact member 6 along resistance 43 will make the currents flowing through coils 40 and 4| unequal, and will result in a deflection of arm 34 from its mid-position. For example, on a deflection of contact member 6 downwardly, corresponding to a decrease in the temperature of the bulb 3 below its normal value, the current aasrsss flowing through relay coil 4| will be increased relatively to current flow through the coil 40 In consequence, the armature 39 will be moved downwardly, bringing arm 34 to the left of the path of edge 32 upon its upward movement. If, on the other hand, the temperature of the bulb 3 increases above its normal value, the contact member 6 will be lifted upwardly along resistance 43, and thereby cause an increase in the current flowing in coil 40 relative to the current flow in coil 4|. This will cause the armature 38 to be moved downwardly and arm 34 to be moved into the path of edge 33.

As cams 2| and 30 rotate in a counter-clockwise direction, the lever I8 and abutment 25 are periodically moved around their pivots to adjust their respective switches. The cams are arranged relative to each other so that during their rotation, abutment 25 will be permitted by cam 30 to turn clockwise under the bias of spring 21 while the roller 20 of lever I8 is still in engagement with the high portion of cam 2|, and consequently the switch I3 is in it open position. As the left end abutment 25 rises, it will or will not be stopped at some point in its movement by engagement of edge 32 or 33 with arm 34, depending upon the position of the latter. As shown in the drawing, the arm 34 has engaged edge 32 to stop the abutment 25 in a horizontal position, and therefore prevent either of the pairs of contacts, at the ends of switch I5, from closing. Continued rotation of the cams will bring the low portion of cam 2| over roller 20 to permit lever II to tilt to close switch |3. Inasmuch as neither pair of contacts in switch |5 is closed, the motor 8 will not be energized. The switch |3 will remain closed a predetermined time depending upon the relative positions of parts 2|a and 2|b of cam 2| and the speed of rotation of the cams.

If the temperature of bulb 3 increases, on the following cycle the arm 34 will be in the path of edge 33, in a manner above described, as the left end of abutment 25 rises, and the abutment will be stopped in such a position that the pair of contacts at the left end of switch |5 will be closed. Subsequently, in the cycle upon the closure of switch |3 by cam 2|, the field 9 of motor 8 will be energized to rotate the motor in such a direction that valve I will be closed to supply less fuel to the heater 2. This same rotation' of the motor will also act to shift contact member 48 downwardly along resistance 41. The resultant movement of the contact 48 tends to make the sum of the portion of resistance 41 between the contact 48 and the conductor 45, and in the portion of the resistance 43 between contact 8 and the conductor 44, equal to the sum of the other portions of the resistances 43 and 41; whereupon the currents flowing through the relay coils 4| and 40 will be made more nearly equal, and the arm 34 will be returned toward its mid-position. Any adjustment of the contact 6 in either direction thus produces a corresponding adjustment of the valve and contact 48 in one direction or the other through the relay 35 and the cam and switch arrangement. These adjustments continue in steps until such time as the temperature of the bulb 3 has re turned to its normal value. At this time, the current flowing in coils 40 and 4| will be equal. and the arm 34 will again move to its midpositi-.n.

Upon a decrease in the temperature in bulb 3, the arm 34 will be moved to the left, and when autment member 25 rises, neither of the edges I or 33 will be engaged by it. Therefore, the butment member 25 can rise until the pair of mta'cts in the right end of switch I are closed. his, when switch I3 is later closed, will energize eld ll) of motor 8 to run it in a direction to open alve I going to furnace 2 and also to move the ontact 48 upwardly along resistance 41.

Continued rotation of cams 2| and 38 will rst open switch l3 and then move abutment iember in a counterclockwise direction to )wer its edges 32 and 33 in preparation for anther cycle.

In the form of the invention. disclosed in Fig. the motor 8, if it is energized due to a devialon of the measured temperature from a desired 'alue, is energized to run a predetermined period f time regardless of the amount of variation in he temperature. lisclosed in Figs. 2 and 3 differs from the above orm in that the motor 8 is run to adjust the 'alve an amount proportional to the deviation vi the temperature from a desired value. This 'orm of the invention is identical to Fig. l in L11 respects but the details of the mechanical 'elay. There is provided a primary abutment nember that determines the direction of rotation )f motor 8 which is responsive to .the position )f arm 34, and there is provided a secondary ibutm'ent member, also responsive to the posi- ;ion of arm 34, to determine the amount of time ;he motor 8 will-be energized.

To the above'end there is provided-a shaft 55 upon which is pivoted a primary abutment memoer 56 which carries the double throw switch l5.

This member 56 has a fiat edge 56a at its left end and is biased in a clockwise direction by spring 51. Also pivoted on shaft 55,and in front of member 56, is a secondary abutment member 58 that has formed thereon a bent- The form of the invention over projection 59 which normally -.overlies the upper edge of member 56. The left end of member 58 is formed with an upwardly extending,

opposed series of steps 68 that are individually adapted to be engaged by arm 34 on their up ward movement. The step that is engaged depends upon the amount and direction of deviation of the arm 34. In front of member 58, and also pivotally mounted on shaft 55, is a bracket 6| for supporting switch I3, the bracket being formed on its left edge with a brake-surface 62. Aicatch mechanism for moving bracket 6| with member 58 on its upward movement'is provided and consists of a lever 63 movable around shaft 55 to the outer end of which is pivoted at 64 a brake-member 65. The brake-member is provided between its ends with a pin 66 and at its outer end with a roller 61 that underlies member 58. Upward movement of the secondary abutment mem r 58 and brake-member 65 is accomplished by ell-crank lever 68, pivoted on shaft 55, and biased in a clockwise direction by spring 69. This bell-crank has a notch 18 formed in its outer end that is adapted to engage pin 66, and is provided between its ends with an overhanging projection '1I that is adapted to engage the top surface of member 58. A cam 12 is mounted on shaft 13, driven at a constant'speed by any suitable source of power, and is used to move the various parts in a counter-clockwise direction against the bias of their respective springs.

In the operation of this form of the invention as the temperature of the bulb 3 varies, the

contact member 6 will be moved along resistance43 and, through the above described circuits, will cause arm 34 to be moved either to the right or to the left, depending upon whether the temperature change was a decrease or an increase. Upon rotation of cam 12, member 56 followed, as shown in Fig. 2, by member 58 will be moved in a clockwise direction by spring 51. If the arm 34 is in its mid-position, or to the left thereof, the edge 56a of member 56 will not engage arm 34 .but will continue to rise until the contacts in the right end of switch ii are closed. If the arm 34 is in its mid-position, indicating normal temperature of the heater, the topmost step 600. of member 58 will engage the arm, and the secondary member 58 will be stopped. In this position of member 58, the bracket 6| and switch l3, moving therewith, are at such an angle that the switch is just about to close.

Continued rotation of cam 12 will let the bellcrank 68 continue to move under the bias of its spring 63 so that the notch 18 encirclingpin 66 will exert an upward force thereon. Since member 58 can no longer move upward, the roller 61 on brake 65 will act as a fulcrum for the brake so that as pin 66 moves up, the roller 61 will move to the right, and brake 65 and lever 63 will move relative to each other to lift the right end of brake 65 from brake-surface 62 of bracket 6|. The bracket 6| and switch l3 will then fall colunter-clockwise under a gravitational bias until they engage stop 14. In this manner, even though a pair of contacts in switch l5 are closed, the motor 8 is not energized since switch l3 was dropped before it was closed. Continued rotation of cam 12 will cause it to engage roller 15 on bell-crank 68 to move the bell-crank clockwise so that clockwise movement of notch 16 will restore lever 68 and brake 65 to their initial positions, andprojection 1| will engage the top edge of member 58 to move it downwardly.

As member 58 moves down, the projection 58 will engage the top edge of member 56 to move it, along with the other parts, downwardly to permit arm 34 to swing free. I

If the temperature of the heater and,. therefore, the bulb 3 is increased, the arm 34, as above described, will be moved to the right. Upon clockwise movement of the member 56, edge 56a will then engage arm 34 and .be stopped in such a position that the pair of contacts in the left end of switch i5 will remain closed, thus determining which field of the motor 8 will be energized. Continued clockwise movement of bell-crank 68 by its spring 68 will, by means of n'otch 10, pin 66, brake 65 and roller 61, lift member 58 until one of the right-hand steps 68 engages arm 34, the particular step depending upon the amount of deviation of the arm. When the member 58, during its clockwise movement, moves just beyond where it would go if arm 34 was in mid-position, the switch |3 will be closed to energize the motor 8, in this condition of the temperature, through field 8. This energization will continue untll member 58 is stopped by engagement of one of the steps 68 and arm 34, and the continued upward movement of pin 66 will remove brake 65 from brake-surface 63 so which the right-hand contacts of switch Hi can close. Upward movement of member 58 is stopped when one of the left hand steps 60 engages arm 34, the deviation of the arm 34 determining which step and therefore the amount of time the motor 8 will be energized before the switch i3 is released so it can drop and open the motor circuit.

From the above detailed description of my invention, it will be seen that I have provided a mechanical relay that is adapted to be used in combination with an electrical proportioning systern to vary the fuel supply to a heater, in order to maintain the temperature of the heater constant. This combination of a proportioning systern and mechanical relay for energizing a motor is very useful, as well as being simple and accurate. The special advantages of this combination include a compact arrangement of parts that are easily assembled in a small space and that do not require any external connections but an ordinary A. C. electric supply line that is obtainable at practically every locality.

It will also be apparent that the type of relay disclosed may be used with any self-balancing measuring system and is not necessarily limited to the proportioning system with which it is disclosed by way of example. For example, the pointer 34 may be movable in response to galvanometer unbalance in an ordinary self-balancing potentiometer circuit.

While in accordance with the provisions of the statutes, I have illustrated and described the best form of my invention now known to me, it will be apparent to those skilled in the art that changes may be made in the form of the apparatus disclosed without departing from the spirit of my invention as set forth in the appended claims, and that certain features of my invention may sometimes be used to advantage without a corresponding use of other features.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In a control instrument the combination with a reversible motor driving means to adjust the value of a controlled condition, a first switch for determining the direction of rotation of said motor, a second energization controlling switch in circuit with said first switch, a balanced electric circuit, means responsive to variations in said controlled condition for unbalancing said circuit, and means for periodically closing said first switch in accordance with said variation and for thereafter periodically closing said second switch to energize said motor.

2. In a control instrument, a double throw switch normally movable in one direction, a cam for periodically moving said switch in another direction, means adapted to interrupt the movement of said switch in said one direction, said means being responsive to variations in a variable condition, a second energization controlling switch, a cam for periodically tilting said second switch, said cams being so timed that the second.

single throw energization controlling switch in circuit with said first-named switch, means to close and open the second mentioned switch between the operations of the first mentioned switch, a reversible motor adapted to be energized when said switches are closed, a balanced electrical circuit, a member responsive to the variation of a condition to unbalance said circuit, means in said circuit determining the throw of said first switch in accordance with said unbalance, and means operated by said motor, when energized, to rebalance said circuit.

4. In a control instrument, a reversible electric motor, a double throw switch for determining the direction of rotation of said motor, a single throw switch in circuit therewith for determining the amount of time said motor is energized, a constantly rotating cam for actuating each switch, said cams being timed to actuate the single throw switch after the double throw switch, a member responsive to variations in a condition, and means regulated by said member for determining the direction of throw of said first switch, whereby said motor will be energized to run in a direction depending upon the variation in said condition.

5. In a control instrument, a first pivoted lever having a switch thereon, a second pivoted lever, a second switch movable therewith, a means responsive to the variations of a condition in the path of movement of said second lever and adapted to be in the path of movement of said first lever or not in accordance with said variations, means to periodically move said first lever and then said second lever to close said switches, movement of said first lever being dominated by said first-named means, and a reversible motor energized by the closing of said switches, to adjust said condition.

6. In a control instrument, a member adjusted into different positions in accordance with variations in a control condition, a device for regulating said condition, a motor for adjusting said device, a first direction controlling switch for said motor, a second time of energization controlling switch for said motor, separate means carrying said switches, means for periodically moving said carrying means into engagement with said member, the carrying means for the first switch being in advance of the carrying means for the second switch whereby to determine the setting of said switches in accordance with the position of said member to determine the direction and time of energization of said motor.

7. In a control instrument, a member movable in accordance with variations in a control condition, a movable lever having a plurality of edges thereon, a direction controlling switch attached to said lever, means for periodically moving said lever toward and from said member, said member engaging one of said edges or not dependent upon the position thereof to thereby set said switch, a motor, said direction-controlling switch being in the motor circuit, a second switch in circuit with said direction-controlling switch and said motor and means for periodically closing said second switch to energize said motor after said direction controlling switch has been set.

8. In a control instrument, a motor, means for periodically energizing said motor comprising a first direction controlling switch, and a second time of energization controlling switch, a member positioned in accordance with variations in a condition to be controlled, means for periodically positioning said first switch in accordance with the position said member and means for thereafter periodically closing said second switch to thereby energize said motor in accordance with the position of said member.

9. In a control instrument, the combination 5 with an element movable in accordance with variations in a condition to be controlled, 9. balanced electrical circuit, means responsive to variations in said condition to unbalance said circuit, a reversible motor to rebalance said circuit, 10

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