US2115831A - Recording galvanometer - Google Patents

Description

May 3, 1938. J. A. WIDMER ,1

RECORDING GALVANOI IETER 7 Original Filed Feb. 17, 1933 3 Sheets-Sheet 1 4C. sour? L IN V EN TOR. JvLEa A WIDMER ATTORNEY V Q y 3, 1938. J. A. WIDMER 2,115,831

nscoxbme GALVANOMETER Original Filed Feb. 17, 19s: 3 Shets-Sheet 2 INVENTOR. Jazz! A. WIDMEB I AT ORNEY y 3, 1938. 4 J. A. WIDMER 2,115,831

nsconnme GALVANOMETER Original Filed Feb. 17, 1935 s She'et-Sheet 5 IN VEN TOR. Juzzs H. MDMER A ORNEY Patented May a, 1m

o es

' ascoanmo osnvsuorm'ran Jules A. Wldmer, Roohester,'N. Y., assignor' to Taylor Instrument Companies, Rochester, N. Y.,

a corporation oi New York Original a cation February 17, 1933, Serial No.

857,233. vided and this application November 26, 1935, Serial No. 51,618

a cums.

This invention relates to control "systems and more particularly to mechanism for use in motor control systems.

" .In various control systems it is necessary to move a member to a predetermined position and to stop this member in that position without any overthrow or oscillating movement about said position. The present invention, therefore, has for its main object the provision of a novel and reliable arrangement which accomplishes this result and which is, nevertheless, simple and economical to manufacture.

In its more specific aspects, the invention includes a galvanometer which mechanically controls the adjustment of switching mechanism whereby a reversible motor is selectively operated to adjust a member to a predetermined point without overthrow and without oscillation about this point.

Referring to the drawings, Fig. l diagrammatically represents a simplified showing of the electrical circuits of an automatic recording pyrometer system; Fig. 2 is a diagrammatic showing of the electrical circuits and certain portions of the mechanical equipment employed in the eter system; and Figs. 3 and 4 are respectively a front elevation and a bottom plan view of the mechanism-for operating a switching deviee under the control of a galvanometer needle.

Referring especially to Fig. 1, there is indicated a conventional potentiometer network generally designated I, which includes the battery 3, the slide wire resistor I, a stationary wiping contaetor I engaging this resistor, the thermocouple I, the galvsnometer 'II and the resistors II and I2. An operating network, controlled in part by the potentiometer network includes a reversible A. C.

the purpose forth.

series 'motor l3 having the field circuits it and I! and the armature II. The circuits of this motor are controlled by a switch generally designated 8 whereby theforward or reverse windings of the motor l3 are connected in circuit to govern the forward, or reverse rotation of this motor. Across .a portion of the operating network there is connected the primary winding ll of transformer l'l, being adjustably connected at tapped points such as "a and a. onthe resistors II and 23, while the secondary winding 04 of this transformer is connected in series with a rectifier l3, for which will be hereinafter set ay' referring to Fig. 2 it will be noted that the reversible motor II has a fly-wheel 2| mounted on its shaft to retard the starting motion of the motor in order to prevent it from reaching a rela- (CI. 7E1) tively high speed on very small temperature changes. The shaft 22 of the motor drives the worm 23 which engages the worm gear 24. This worm gear, which rotates on the axis 25, carries the slide wire resistor I to change the relation of this element with respect to the stationary wiper I, and also carries a drum 26 which drives a metal tape 21 carrying a stylus 28. The movement of this tape is guided by the rollers 29 and 30 to move the stylus 28 transversely across the chart 3i, which is driven by a rotating roll 32 carried by the shaft 33. This shaft is driven by the worm thus continuously driven, carries the rotating cams 40, ll, and 42. As best shown in Fig. 3, the cam til operates the link 43 by a reciprocating motion. This link is provided-with a slot 44 to receive the shaft 36 and is also provided with a. roller or cam follower 45 to engage the periphery of the cam 40. The link 43 at its left end, as herein illustrated, is pivoted at 46 to an arm 41, the upper end of which is secured to one end of the sleeve 48 having a portion passing through a bearing in the supporting plate 49. At the other end of this sleeve there is secured a cam plate 50 notched at its upper edge as indicated at 5i to engage a pin 52. The pin 62 is carried by a stepped lever 53 pivoted in a suitable support (not shown) at point 54. The left end of this lever is so shaped that its upper edge is formed relatively close together, to restrict the swinging of the galvanometer needle to a very small movement in order that it may respond quickly. Thus these stops serve to keep the galvanometer needle very close to the center point between the stops, even in cases wherein their absence the galvanometer needle would have a large deflection. By this arrangement the galvanometer needle can return to its center position in a minimum amount of time when the current through the galvanometer coil is reduced to zero. The right hand portion of the lever 53 has connected thereto athin flat spring which has fastened thereto the notched shutter plate 6 I f It should be pointed out that the right hand end of the lever 33 is heavier than the left hand end so that when the pin I2 is not supported by the cam 58, the right end of the lever will drop until some one of the portions 55,

88 or 51. at the left end thereof restsagainst the galvanometer needle 88. As shown in Fig. 4, a plate 88 is supported on the upper ends of the stops 58 so that when the lever 58 is elevated to engage the end of the galvanometer needle, this needle, although it is elevated slightly, is held against abnormal upward movement by this plate.

It has been mentioned that the rotating shaft 88 carries cams H and 42. Cam 42-is engaged by the cam follower II mounted on the lever I2 which lever is pivoted at its right hand end on the shaft 84. The free end of the lever I2 is formedwith steps as shown at 85a and 85b to engage the shutter plate 8|. Near the free end of this lever there is provided a pin I8 which engages the slot 81 in the link 88. The upper end of this link is pivoted at 88a to the switch actuating arm 88 which arm is pivoted at 18. The cam 4| is engaged by the cam follower 82 carried by the lever 88 which is pivoted at its right hand end on shaft 84. The free end of the lever 88- is formed with steps the same in shape as thoseon the free end of the lever I2 and likewise cooperates with the shutter plate 8|. Near the free end of the lever 83 there is likewise provided a pin 88 which is received in a slot I4 in the lower end of the link I5, the upper end of which link is pivoted at 1511 to the arm 89. The

free end of the arm 88 has a drum portion I8 a series of normally open contactor springs Sid and 820, etc., to bring them into closed condition.

By way of example, it isassumed that shaft 88 rotating at a speed of- R. P. M. will cause the left end of the lever 53 to be raised and lowered once every second, through the action of the members including the lever 43 and the cam plate 50 engaging the pin 52. This motion of the lever 58 takes place in about one quarter of a second and its left end remains in its lowered position about three quarters of a second. During this last interval of time the galvanometer needle 581s free to swing and if the potentiometer network 5 is balanced, the galvanometer needle 58 will remain in its intermediate position, that is, in the notch 51. If, however, the potentiometer network is unbalanced during this period of unrestricted swing of the galvanometer needle 58, this needle will be deflected to the left or to the right, as the case may be, until it rests against one of the stops 58. If it be assumed that the galvanometer needle 58 has been deflected to the left, the lever 53 when next released under the action of cam plate 58 will contact with the galvanometer needle 58 at step 58. However, if the galvanometer needle is deflected to the right, the part 55 of the lever 58 will engage the galvanometer needle. Thus these three possible positions of the lever 53 provide three different ways of obstructing the motion of levers 88 and I2. The cams 4| and 42 are identical and hold the levers 83 and I2 in the position shown in Fig. 3 for the greater part of each of their revolutions,

that is to say, for about seven-eights of a second.

During the remaining one-eighth of a second the notches in these cams permit the levers 83 and I2 to rotate upward around shaft 84 under the control of springs such as 82. This motion of these levers, however, can only take place when the two slots in the plate 48 are unrestricted by the shutter plate 8|. It has been mentioned that and 4, both of the slots in plate 48 are partially obstructed so that the levers 88 and I2 may rotate a small angle until steps 85b thereof rest against the shutter plate. In the second position of the'shutter plate, the upper slot (Fig. '4) in plate 48 is unobstructed while the lower slot thereof is completely obstructed so that lever I2 passes completely through the slot while the step 85a of lever rests against the shutter and keeps this lever in its original position. In the third position of the shutter plate, the last-named conditions with respect to the shutter plate are reversed so that the lever 88 passes through the lower slot and lever I2 remains stationary. The notches in the cams 4| and 42 and in the cam 48 are so timed that the motion of the levers 88 and I2, requiring. about one-eighth of a second,

occurs within the quarter second period during -is pivoted at III to rock the drum I8 with the projections 11 to 88 inclusive, to various positions, thereby closing various pairs of springs 'or contacts 9| and 82 (Fig. 2) to complete different circuit combinations in the networks of Figs. 1 and 2. The drum and the pairs of springs actuated thereby constitute a multiposition progressively movable switching means.

The operation of the systemis as follows: As long as the potentiometer network 8 is balanced, the galvanometer needle 58 remains in the position shown in Fig. 4, that is, in engagement with the notch 51 of lever 58. with the lever 88 in this position, the levers 83 and I2 will actuate switch arm 89 with the result that either the projection I8 or I8 will be positioned to close contact between springs 82b and either springs Me or Sld, while springs 82a and 82c are open so that the motor remains at rest.

However, if the temperature to which the thermocouple 8 is exposed changes, the potential across this thermocouple changes and unbalances the potentiometer network thereby causing current to flow through the galvanometer coil and resistors II and I2 with the result that the galvanometer needle 58 will be deflected from its intermediate position. If it be assumed that the galvanometer needle is deflected toward the left, the switch drum I8 will be operated to close the two pairs of switch springs, 82c with Me and 92a with Sla, as indicated in Fig. 1. The closing of these springs will immediately cause the motor I3 to operate in a circuit traceable from the alternating current source, conductor 85, spring 82a, spring 8la, motor field I4, armature I8, resistor I 8, conductor 88, to the other side of the A. C. source. The motor I8 willrotate the slide wire resistor I with respect to the contact 8 in the proper direction untilthe potentiometer network is again balanced. On the establishing of this balanced condition, the needle 58 will then return to its intermediate position and consequently the switch arm through the action of links 88, I5 and the levers 88 and I2, will be moved to a position where the switch drum I8 will be restored to one of its intermethe operating circuit of the motor lust described is interrupted and at the some time the motor. is short-circuited over a path traceable from the lower terminal oi. the armature ll, conductor 81, spring 02b, spring Ole, iield windim II, and the upper terminal oi the armature, which circuit causes the motorto become a sbort-circiuted generator, thereby acting as a powerful brake. Therefore; when the switch is moved to open the operating circuit 0! the'motor, the motor will be'stopped very quickly. Ina similar manner, the reverse operation of the system is eiiected, that is, the motor II will operate in the opposite direction when the galvanometer needle II is deflected toward the right. i

In order to prevent overthrow oi the stylus 28, an anticipating arrangement is provided in the system oi'this invention. As herein disclosed, this arrangement consists of an auxiliary circuit including the resistors II and 2| which are tapped at the points Ila and lla'ior connection with the primary winding ll of a small transformer II. The secondary winding ll of this transformer is connected in series with rectifier SI and through springs 02c and springs Ole or 0|! with either resistor II or l2. It will be understood that the primary winding of the transformer I1 is energized through the potential diiIerence between the taps "a and 20a. The current thus induced in the secondary winding of this transformer after passing through the rectifier 98 and the springs Me in engagement with spring Qle or 9!! through either the resistor H or II, flows back to the secondary winding 94 of the trans former. If, for example, spring 920 is in engagement with spring lie, current flowing in the lastdescribed anticipatingcircuit including the resistor II, will develop a diflerence in potential across this resistor in the same direction as the difference of potential set up across this resistor, due to current flowing therethrough in the previously mentioned circuit including thermocouple 9, the resistors l2 and II and the galvanometer coil. The difference in potential established by the anticipating circuit and the resulting current, increase thediflerence' in potential across the resistor II and thereby decrease the current through the thermocouple l and the galvanometer l0, so that the galvanometer needle swings to its zero position sooner than it would otherwise. The connections are so made that this anticipatory eflect will always tend to advance the galvanometer needle 58 toward its normal intermediate position, so that the needle will reach this position a short time before the potentiometer slide wire I has reached the balance point. Through the switch mechanism previously described, the motor operating circuit will be opened before the balance point is reached, but the motor will continue to operate due to the inertia of the armature it until the braking action resulting from the short circuit, as well as friction of all of the moving parts bring it to a stop. The anticipatory arrangement should be so designed as to bring the motor from full speed to a complete stop either at the exact balance point of the slide wire or very slightly before this point is reached.

It will be appreciated that with small deflections of short duration of the galvanometer needle 58, the motor does, not reach full speed and the motor current is therefore higher than the full speed'current, However, as the motor speed increases, the motor current decreases and will cause a corresponding change in the difference of potential between the taps Ila and 20a. Consequently, the potential-in the anticipatory circuit will vary gradually and by selecting proper resistance values for resistors II and II and with suitable location of the taps "a and a, the anticipatory efl'ect' can be so designed as to operate eiIectively for large as well as for small galvanometer deflections. From the foregoing disclosure it will be seen that the mechanical devices forming a part of this invention are of rugged construction, and include unusually few bard application, Serial No. 657,232, flied Feb.

17, 1933, originally flled in the names 0! Hubbard and Widmer, now Patent No. 2,025,749, granted December 31, 1935.

I claim:

1. In a device of the class described, an instrument provided with a movable index, an oscillatably mounted strip having a notched side edge and a slotted end portion, means for periodically moving the notched edge of said strip into engagement with said index to position said strip in accordance with the setting oi. said index, said strip being movable at right angles to the plane of movement of said index, rotatively mounted elements periodically movable in timed relation to the periodic movement of said strip, said elements being movable into engagement with the slotted end portion of said strip in accordance with the position oi. the slotted portion thereof, a pivoted member to be positioned, and links respectively connected to said member at opposite sides of said pivot and to said elements for selectively positioning said member.

2. In a device 01' the class described, an instrument provided with a movable index, an oscillatably mounted strip having a notched edge and, a slotted end portion, means including a cam for periodically moving the notched edge of said strip into engagement with said index to position said strip in accordance with the setting of said index, said strip being movable across the plane of movement of said index, elements selectively movable into engagement or out of engagement with said strip in accordance with the position of the slotted portion of said strip, cam means for moving said elements periodically in timed relation to the periodic movement of said strip, a single rotating shaft on which said cam and said cam means are mounted, a member to be positioned, and means controlled by said elements for selectively positioning said member.

3. In a device of the class described, an instrument provided with a. movable index, a. strip having a notched side portion and a slotted end portion, means for periodically moving the notched portion of said strip into engagement with said index, elements selectively movable to positions determined by their engagement with or by their lack of engagement with said slotted portions in accordance with the position of said strip, a movable member, and means including said elements for selectively positioning said member.

4. In a device of the class described, a galvanometer provided with a swing needle, an oscillatable strip having a notched portion. and a slotted portion, means for periodically moving the notched portion of said strip into engagement with said needle to position said strip in accordance with the setting or said needle, said strip being movable in a plane. intersecting the plane of movement of said needle, elements selectively movable in a plane at right angles to the plane of movement of said strip, said elements being movable to positions determined by their engagement with or by their lack of engagement with said slotted portion in accordance with the position of said strip, a member, and means including said elements for selectively positioning said member.

5. In a device of the class described, an instrument provided with a movable index, a strip having a notched edge and a slotted portion, means for periodically moving the notched edge 01' said strip into engagement with said index to position said strip in accordance with the setting of said index, said strip being movable in a plane intersecting the plane of movement of said index, oscillatably mounted elements selectively movable in a plane intersecting the plane of movement. of said strip, said elements being movable in accordance with the position oi the slotted portion of said strip, a pivoted member to be positioned, and links respectively interconnecting the end portions of said member and said elements for selectively positioning said member.

6. In a device of the class described, an instrument provided with a movable index, an oscillatably mounted strip having a. notched edge and a slotted portion, means for periodically moving the notched edge of said strip into engagement with said index to position said strip in accordance with the setting of said index, said strip being movable at right angles to the plane of movement of "said index, elements periodically movable in timed relation to the periodic movement of said strip, said elements being movable in accordance with the position of the slotted portion oi said strip, a pivoted member to be positioned, and links respectively connected to said member at opposite sides of said pivot and to said elements for selectively positioning said member.

JULES A. WIDLER.

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