US3391331A - Voltage regulating system - Google Patents

Description

July 2, 1968 J. FRENCH 3,391,331

VOLTAGE REGULATING SYSTEM Filed Oct. 14, 1964 5 Sheets-Sheet INVENTOR JOHN F. FRENCH Emu 56. Watt y 1968 J. F. FRENCH 3,391,331

VOLTAGE REGULATING SYSTEM Filed Oct. 14. 1964 3 Sheets-Sheet z INVENTOQ JOHN F. FRENCH 3 Sheets-Sheet 5 Filed Oct. 14, 1964 INVENTOR.

JOHN F. FRENCH 5% may N Em United States Patent 3,391,331 VOLTAGE REGULATING SYSTEM John F. French, Aurora, [1]., assignor to Edward Davis, Chicago, Ill. Filed Oct. 14, 1964, Ser. No. 403,759 Claims. (Cl. 323-22) ABSTRACT OF THE DISCLOSURE A voltage regulating system including a control circuit for a silicon controlled rectifier which is connected between an AC power source and the primary winding of a power transformer. The control circuit fires the silicon controlled rectifier at progressively sooner intervals during successive half-cycles of the AC source to increase the transformers power capabilities in successive stages beyond its rated capacity, by minimizing its subjection to severe mechanical shock.

The present invention relates to improvements in machines for stress relieving wire coil springs and is more particularly concerned with the novel construction and assembly of such machine and the electrical control therefor.

More specifically, the invention is concerned with a stress relieving attachment for spring coiling machines, particularly of the type used for coiling pig-tail springs, and it includes novel means to receive coiled springs in rapid succession directly from the forming machine and clamping them in a position to be engaged at opposite ends by electrodes which supply electric current thereto for predetermined periods of time and to thereafter dischange said springs. The electrodes have associated with them novel means to insure dissipation of heat generated. The clamp and electrodes are readily adjustable to adapt the machine for heat treating springs of various diameters and length.

It is therefore an object of the invention to automatically stress-relieve coiled springs by resistance heating in their normal passage through the forming machine.

Another object is to automatically provide means for accurate control of the stress-relieving temperature achieved as a function of resistance heating.

Another object is to control the stress-relieving current by the use of a silicon controlled rectifier.

Another object is to provide means whereby the electrodes are kept cool.

Another object is to provide finished springs of constant and uniform dimensions.

Another object is to provide novel means to freely adjust the electrodes so as to provide new wearing surfaces to the spring as required.

Another object is to provide electronic control circuitry which is modular in design so as to be serviced when necessary by an individual without advanced electronic training.

Another object is to provide means of controlling primary line current by means. of closed loop feedback.

Another object is to provide novel clamp jaw assemblies whereby each clamping assembly and associated electrode is independently adjustable with respect to the other to adapt them to accommodate any configuration of spring which the basic machine is capable of forming.

Another object is to provide means whereby accessory controls, such as optical pyrometers, may be used to control stress-relieving temperature with extreme accuracy.

Another object is to provide a stress-relieving attachment for spring coiling machines.

Another object is to provide novel means and apparatus for stress-relieving pig-tail springs.

3,391,331 Patented July 2, 1968 "ice brAnother object is to provide novel clamp jaw assem- 1es.

The structure by means of which the above noted and other advantages and objects of the invention are attained will be described in the following specification, taken in conjunction with the accompanying drawings, showing a preferred illustrative embodiment of the invention, in which:

FIG. 1 is a front elevational view of the stress-relieving attachment.

FIG. 2 is a side elevational view as viewed along line 22 of FIG. 1.

FIG. 3 is an enlarged sectional view, taken along line 33 of FIG. 2.

FIG. 4 is a schematic of the electric wiring.

Referring now to the exemplary disclosure of the invention shown in the accompanying drawings, and particularly in FIG. 1, the springs are formed in a machine of conventional construction which includes a feed clamp arm 11 journalled at 12 and into which a newly formed spring A is advanced. At a select cycle of operation, the feed clamp arm rocks in a counterclockwise direction to carry the spring upwardly through an are substantially into the position occupied by spring B. When the spring is in the B position, it is engaged near its ends by novel pneumatically operated clamp mechanisms 13 and 14 each of which has associated with it, as better explained hereinafter, an electrode adapted to receive electric C1111- rent, at predetermined intervals and for a predetermined period of time, for passage through the spring and heating same. The clamp-electrode assemblies are mounted in a frame structure that includes an upstanding support plate 15 that is attached firmly, as at 16, to the frame of the spring forming machine (not shown). This assembly is operated in conjunction with operation of the spring forming machine so that each time a spring is formed, and this occurs with great rapidity, the formed spring is thrust forward into the feed clamp arm 11 which then carries it to the electrode-clamp assemblies which immediately function to heat the spring which is then discharged onto a conveyor track 17 or other means for conveying the stress-relieved spring away from the machine.

Referring specifically to FIGS. 2 and 3, which depict the electrode-clamp means 13 for engaging the knotted end of the spring B, said means includes an aluminum block 18 that is secured firmly to the plate 15 and has a plurality of heat dissipating fins 19 on its front face. A pneumatic piston-cylinder assembly 21, having an air line connected at each end, as at 22, 23, is secured firmly to the back face of block 18 and its piston rod 24 extends freely through said block. A clamp arm 25, pivoted on said block at 26, has its upper end pivotally attached to said piston rod, as at 27, and its other or depending end is offset rearwardly to provide a clamp jaw 28. This jaw, when in clamping position engages with the base or knotted end of the coil spring B and clamps it firmly against an electrode 29 mounted for adjustment and easy replacement in the block 18. Although the electrode may be mounted in any convenient manner it preferably seats in a slot 30 in said block and is held firmly in an adjusted position as by screws 31.

Obviously, the clamp is moved into and out of clamping position by the admittance of air pressure into the respective ends of cylinder 21. Such air flow is electrically controlled and is cycled tothe machine cycle. As more fully explained hereinafter, it is timed to clamp the spring prior to flowing electric current to the electrode and to release the spring after the current flow to the electrode has been cut off. This prevents the formation of an electric are at the point of contact of the spring with the electrode.

The tail end of spring B is, simultaneously to engagement of clamp jaw 23 with the knotted end of the spring, clamped in the electrode-clamp means 14, located on the front side of the machine. This means is best shown in FIG. 2 and it comprises an aluminum block 32 having heat dissipating fins 33 on its upper face. The block is secured firmly to a wall 34 of insulation material that is connected firmly to and held in place by a cross bar 35 supported in spaced relation from plate 15, as by means of tie rods 36. The wall 34 can be adjusted vertically, horizontally and laterally to accommodate springs of various diameters.

Mounted firmly on the bottom face of block 32 is a pneumatic piston-cylinder assembly 37 having connection at each end with a source of air pressure through conduits 38. A piston rod 39 extends out of said assembly and it is pivotally connected, as at 41, to a clamp knuckle 42. This knuckle has an arcua'te rack 43 concentric with said pivot 41, which is meshed with a rack 44 on the bottom face of block 32. The knuckle includes a clamp jaw 45 disposed, when in one position, to engage over and clamp the tail end of spring B firmly against an electrode 46 carried by block 32. In operation, to move the clamp jaw 45 out of engagement with the spring, the piston rod is drawn into the cylinder. This rotates the knuckle about its pivot 41 into substantially the dotted line position shown. It should be noted that the knuckle is such that it is withdrawn clear of the spring end when in unclamped position. Movement of the knuckle into clamping and unclamping positions is cycled so as to clamp and unclamp the spring prior to and after, respectively, current is supplied to the electrode so as to prevent electric arcing.

In FIG. 4, a circuit incorporating the principles of the present invention for stress relieving heavy wire coils is indicated generally by the reference character 47. The circuit 47 includes the leads L1, L2, and L3 with the leads L1 and L2 connected to a 230 v., 100 amp AC supply and lead L3 serving as a neutral.

Lead L1 extends to one terminal of the primary of a stress relief transformer T1, whose secondary is connected to the pair of electrodes 29 and 46. As stated, the electrodes 29 and 46 are adapted to be clamped to opposite ends of the coil B, which is to be stress relieved, after the coil is formed. Since this transformer T1 must draw considerable power and is subject to considerable heat, a fan 48 connected between leads L1 and L3 is provided to cool the transformer and a thermistor THl is provided for temperature sensing of the transformer condition. A meter M1 is connected across the primary of transformer T1.

The other terminal of transformer T1 is connected to the anode of a silicon controlled rectifier SCRl through a positively poled rectifier or diode D1 and is also connected to the cathode of SCRl through a negatively poled diode D2. The anode of SCRl and the negative pole of diode D1 are also connected to lead L2 through a positively poled diode D3, while the cathode of SCR1 and the positive terminal of diode D2 are connected to lead L2 through a positively poled diode D4. The diodes or unidirectional circuit elements D1, D2, D3 and D4 are thus connected in a rectifier bridge arrangement in which current cannot flow between the end terminals and leads L1 and L2 unless SCRI is fired. The SCRI therefore serves as a gate for the transformer T1.

A pair of controlled avalanche silicon rectifiers CASR1 and CASR2 are connected between leads L1 and L2 to protect the diodes D1, D2, D3 and D4 together with SCRl from transients appearing across the lines. The silicon controlled rectifier SCRI has a control electrode E3 and it together with the cathode of SCRl are connected to the output of a gate circuit indicated generally at G1.

The gate circuit G1 is controlled during each successive half cycle of AC current on lead L1 as will be explained. The gate circuit G1 enables SCR1 to fire for passing current through the primary of transformer T1 and thereby enable stress relief of the coil connected across electrodes 29 and 46.

Thus, lead L1 also extends through normally closed form C contacts Kla of an alarm relay Kl to one terminal of the normally open contacts S1 controlled by a cam C1. A lamp PL1 connected between the normally closed contacts Kla and lead L3 serves to indicate contacts Kla are closed. The other terminal of contacts S1 extend through the primary of a transformer T2 to lead L3. Transformer T2 is adapted to supply power to gate circuit G1.

In addition, lead L1 extends to one terminal of normally open contacts S2 which are under control of a second cam C2. The other termnial of contacts S2 is connected through a solenoid SR1 to the neutral lead L3. Cams C1 and C2 are adapted to be operated together for closing switches S1 and S2, when the machine has completed its coil forming operation on a wire segment and the coil is positioned at the stress relief station between electrodes 29 and 46. Solenoid SR1 operates at that time to cause electrodes 29 and 46 to be clamped to opposite ends of the coil.

The output of transformer T2 is approximately 35 v., for example, and is applied to a rectifier bridge R31 in gate circuit G1. The positive output terminal of bridge RBI is connected through a 3.3K resistor R1 and diode D5 over a lead L6 to one terminal of a potentiometer P1 and the negative output is connected to a lead L7. The gate circuit G1 also includes a transistor TR1 whose emitter circuit is connected to lead L6 through a 432 ohm resistor R2 and to lead L7 through a 22K resistor R3. The base circuit of transistor TRl is connected to a 60K resistor R4 to the arm of potentiometer P1 and a 200 t. capacitor Cla connects the junction of the potentiometer arm and resistor R4 to lead L6. The other terminal of potentiometer P1 is connected through a 4.7K resistor R5 to lead L7. Thus adjustment of the potentiometer P1 serves to control the RC time constant of the potential applied to the base circuit of transistor TR1 which may be, for example, a 2N525.

The collector circuit of transistor TR1 is connected to the emitter of a unijunction transistor UT1 whose base circuits are respectively connected through a ohm resistor R7 to the junction of resistor R1 and diode D5 and through the primary of an output pulse transformer T3 and a 22 ohm resistor R8 to lead L7. A clamp diode D7 is connected in shunt with transformer T3, transistor UT1 and resistors R7 and R8. The junction of the emitter circuit of UT1 and the collector circuit of TRl is also connected to one terminal of a .22 ,uf. capacitor C2a whose other terminal is connected to lead L7.

Thus transistor UT1 conducts or fires when the positive bias on its emitter circuit exceeds its stand-off ratio, and this in turn depends on the time period in which capacitor C2a is charged to this value. The time period for the charge on capacitor GM to increase varies in proportion to the conduction of transistor TRI. The conduction of TR1 in turn depends on the RC constant of potentiometer P1 and capacitor Cla. Therefore, the points at which UT1 conducts during each half-cycle of AC applied to bridge RBI occurs at a progressively suitable interval as capacitor Cla charges to progressively higher values. This point is therefore determined by the setting of potentiometer P1 which may be manually adjusted to secure a desired output from transformer T1.

The output of transformer T3 is connected over leads L4 and L5 across the control electrode and cathode of SCR1 for firing the SCR. The SCRl therefore fires at a progressively shorter interval after the start or intiation of each successive half cycle applied to gate circuit G1 due to the decreasing time necessary to charge capacitor C2a to the stand off ratio.

Thus, the transformer T1 is enabled to withstand peak power loads of many times its rated value. For example, over a 20 kva. input may be applied to the transformer T1 rated at 5 kva., as these loads are applied intermittently while the mechanical shock resulting from the application of the loads is minimized during the successive cycles instead of being instantaneously applied.

The thermistor THl has one terminal connected through relay K1 to the negative output terminal of a rectifier bridge RB2. The positive output terminal of rectifier bridge RB2 is connected through a 1K resistor R9 and an adjustable resistor R10 to the other terminal of transistor TH1. Input power to the bridge RBZ is supplied by a 12 volt output transformer T4 whose primary is connected between leads L1 and L3.

Thus, if transformer T1 becomes overheated this is detected by a change in the voltage drop across THl, which enables relay K1 to operate contacts Kla. When contacts Kla switch, lamp PL1 is extinguished. Transformer T2 is simultaneously deenergized to prevent the gate circuit G1 from enabling energization of transformer T1 while lamp PL2 is lighted to signal this condition. Other alarm features may include a pyrometer or other temperature sensing element for monitoring the spring temperature.

As each coil is completed and is positioned at the stress relief station, the cams C1 and C2 operate to close contacts S1 and S2 respectively. Contacts S2 on closing connect solenoid SR1 across leads L1 and L3 and the solenoid energizes to clamp the electrodes 29 and 46 to opposite ends of the coil B. The transformer T1 however, does not pass current, since the SCRl is extinguished.

Simultaneously, contacts S1 on closing energizes the primary of transformer T2 and it supplies approximately 35 v. through the bridge rectifier RBI to the gate circuit G1. Capacitor Cla therefore starts to charge in a positive direction and positive potential is thereafter supplied to the emitter circuit of transistor TRl. The base circuit of transistor TR1 starts to swing positive at a rate dependent on the RC time constant of capacitor C1a and potentiometer P1 and it conducts after the start of the power cycle applied to lead L1.

As the base of transistor TR1 starts to swing positive, it conducts at a heavier rate to charge capacitor C2a in a positive direction. This causes UT1 to fire. As this occurs, the transformer T3 provides an output pulse to fire SCRl and transformer T1 therefore receives its first power pulse considerably after the start of the corresponding cycle applied across leads L1 and L2.

Between cycles capacitor C2a is effectively discharged. The voltage on capacitor Cla increases to progressively higher levels on each half cycle since its RC time constant is larger and it cannot discharge completely during each successive cycle. Therefore, on each successive half cycle TRl will conduct more heavily to charge C2a more rapidly to a level sufiicient to fire UT1 at progressively shorter intervals at each half cycle. The SCR1 is therefore fired at correspondingly sooner intervals so that transformer T1 is gradually brought into peak power delivery.

After a predetermined interval cams C1 and C2 open contacts S1 and S2 to deenergize the gate circuit G1 and solenoid SR1. SCR1 therefore, remain extinguished until the next coil is brought into position for clamping while the stress relieved coil is passed to the succeeding station.

Although I have described a preferred embodiment of my invention, in considerable detail, it will be understood that the description thereof is intended to be illustrative, rather than restrictive, as many details of the strucure and circuitry disclosed may be modified or changed without departing from the spirit or scope of the invention. Accordingly, I do not desire to be restricted to the exact construction described.

I claim:

1. A circuit for energizing a transformer whose primary is connected between a pair of leads adapted to provide power substantially in excess of the rated capacity of said transformer to enable stress relief of a metal coil, the improvement comprising a normally closed gate connected between one of said leads and said primary and normally preventing current flow through said primary, and means controlled responsive to successive half cycles of AC current appearing on the other of said leads for opening said gate at progressively shorter intervals after initiation of each half cycle whereby the power applied to said transformer is increased in successive stages.

2. In the circuit claimed in claim 1, means operatively connected to the gate opening means for enabling opening thereof only during the positioning of a load across the output of said transformer.

3. In the circuit claimed in claim 1, a temperature sensing element for sensing the heat rise in said transformer, and means connected to said gate opening means for preventing opening thereof upon said temperature rising above a predetermined level.

4. The circuit claimed in claim 1, in which said means comprise an amplifying device having a control electrode controlled in response to the appearance of each successive half cycle for causing said amplifying device to conduct at progressively higher levels and in which said gate comprises a silicon controlled rectifier having a control electrode coupled to the output of said amplifying device.

5. The circuit claimed in claim 1, in which said means comprises an adjustable RC circuit adapted to be energized on each of said successive half cycles, a capacitor, an electronic valve controlled by said RC circuit to charge said capacitor at progressively shorter time intervals after initiation of each successive half cycle.

6. A circuit for energizing a transformer whose primary is connected between a pair of leads adapted to provide power substantially in excess of the rated capacity of said transformer to enable stress relief of a metal segment, the improvement comprising a normally closed gate connected to said primary and normally preventing current flow through said primary, and means controlled responsive to AC current appearing on one of said leads for opening said gate at progressively shorter intervals after initiation of respective half cycles of AC current whereby the power applied to said transformer is increased in successive stages.

7. A circuit for energizing a transformer having a primary connected between a pair of leads adapted to provide power substantially in excess of the rated capacity of said transformer for stress relief of a metal strip, the improvement comprising a silicon controlled rectifier connected between one of said leads and said primary and normally extinguished for preventing current flow through said primary, means for passing current only in response to each successive AC cycle appearing on the other of said leads, including a transistor having base, emitter and collector circuits, means rendering said transistor conductive at higher conduction rates after the start of each successive cycle, a capacitor connected in series with said emitter and collector circuits and adapted to be charged thereby at progressively shorter intervals, means responsive to a predetermined charge level on said capacitor for firing said silicon controlled rectifier at progressively shorter intervals after the initiation of each successive cycle, whereby the power applied to said transformer is increased in successive stages, and means for enabling the energization of said current passing means only during the positioning of a load across the output of said transformer.

8. A circuit for energizing a transformer having a primary connected between a pair of leads adapted to provide power at least several times greater than the rated capacity of said transformer for stress relief of a metal strip, the improvement comprising a rectifier bridge having end terminals of each leg connected between one of said leads and said primary and adapted to prevent the flow of current therebetween along any one leg, a normally extinguished silicon controlled rectifier connected across the legs of said bridge and enabling the passage of current from either of said leads to the other lead and through said primary only when said silicon controlled rectifier is fired, means for deriving a DC potential during successive half cycles of A.C. appearing on the other of said leads, means adapted to conduct current on the derivation of said DC. potential at a level dependent on the level of the biasing potential applied thereto, a capacitor connected to said current conducting means adapted to be charged to suecessively higher levels on each of said successive half cycles for raising said biasing potential accordingly, and means interconnecting the output of said conductive means with the control electrode circuit of said silicon controlled rectifier whereby said silicon controlled rectifier is caused to fire at progressively shorter intervals after the initiation of each alternate half cycle applied to said rectifier bridge whereby the power applied to said transformer is increased in successive stages.

9. A circuit for energizing a transformer whose primary is connected between a pair of leads adapted to supply power to said primary substantially greater than the power rating of said transformer for enabling the stress relief of a metal coil adapted to be connected across the secondary of said transformer, the improvement comprising a silicon controlled rectifier having a control electrode and connected between one of said leads and said primary and normally preventing current fiow between said leads and through said primary, a rectifier arrangement connected across said Silicon controlled rectifier for enabling the passage of current from either of said leads to the other lead and through said primary only when said silicon controlled rectifier is fired, means for deriving a DC). potential during successive half cycles of A.C. appearing on the other of said leads, a transistor having base, emitter and collector circuits with said emitter and collector circuits connected across said means, a capacitor connected across said transistor base and emitter adapted to be charged to progressively higher levels on each successive A.C. half cycle for controlling the conduction level of said transistor accordingly, a unijunction transistor having base circuits connected across said means and an emitter circuit connected to the collector circuit of said one transistor, and adapted to be fired at progressively sooner intervals in response to the conduction level of said transistor, means interconnecting one of said unijunction base circuits with said control electrode of said silicon controlled rectifier whereby said silicon controlled rectifier is caused to fire at progressively sooner intervals during each successive half cycle applied to said rectifier bridge whereby the power applied to said transformer is increased in successive stages.

10. A circuit for energizing a 5 kva. transformer having a primary adapted to be connected across a pair of leads arranged to supply at least 20 kva. for enabling said transformer to stress relieve a metal coil, the improvement comprising a silicon controlled rectifier having a control electrode and connected between one of said leads and said primary and normally preventing current flow between said leads and through said primary, a rectifier arrangement connected across said silicon controlled rectifier for enabling the passage of current from either of said leads to the other lead and through said primary only when said silicon controlled rectifier is fired, a rectifier bridge adapted to derive a DC. potential during successive half cycles of A.C. appearing on the other of said leads, a plurality of resistors connected across said bridge, one transistor having base, emitter and collector circuits with said emitter circuit connected to one terminal of said bridge through a junction between said plurality of resistors, a unijunction transistor having base circuits connected across said bridge and an emitter circuit connected to the collector circuit of said transistor, a capacitor connected between said collector circuit and another terminal of said bridge, an adjustable RC circuit connected across said bridge and to the base circuit of said one transistor for controlling the conduction of said one transistor whereby the charge on said capacitor is caused to reach a predetermined value at a progressively sooner interval in each successive half cycle appearing on said one lead, means interconnecting one of said unijunction base circuits with the control electrode of said silicon controlled rectifier whereby said silicon controlled rectifier is caused to fire at progressively shorter intervals during each successive half cycle applied to said rectifier bridge whereby the power applied to said transformer is increased in successive stages, and means for enabling said bridge to supply said D.C. only during the positioning of a load across the secondary of said transformer.

References Cited UNITED STATES PATENTS 2,623,168 12/1952 Stadum et al. 2l9-50 X 2,739,281 3/ 1956 Rockafellow 323-18 3,036,260 5/1962 Berweger 32318 X 3,275,802 9/1966 Vandivere et al 219-499 3,307,093 2/1967 Wright 3l8-227 X JOHN F. COUCH, Primary Examiner. W. E. RAY, Examiner.

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