US2515314A - Electrical control device - Google Patents

Description

July 18, 1950 R. T. PIERCE ELECTRICAL CONTROL DEVICE Filed Sept. 23, 1946 Magnetic Non-Magnetic Ta Control/ed Device l a m 8 I 5 a M 4 a 3 3 Patented July 18, 1950 ELECTRICAL CONTROL DEVICE Raymond T. Pierce, Millburn, N. .L, assignor to Weston Electrical Instrument Corporation, Newark, N. .l., a corporation of New Jersey Application September 23, 1946, Serial No. 698,676

4 Claims. (01. 175-s20 i This invention relates to electrical control de- I vices and particularly to control devices of the type in which a sensitive instrument relay responsive to small current values is used to control a load circuit carrying substantial power.

An object of the invention is to provide electrical control devices including a magnetic contact type relay having a contact arm movable between spaced stationary contacts, and a solenoid for resetting the magnetic contacts and controlling a load circuit.

A more specific object is to provide an instrument relay of the magnetic pull-in type and a solenoid energized thereby when the relay contact arm has moved a predetermined distance in one direction; the arrangement being such that motion ofthe solenoid armature closes a holding circuit for the solenoid and resets the instrument relay by separating the magnetic contacts, the solenoid then remaining in the energized condition until the relay contact arm moves a predetermined distance in the other direction momentarily to short-circuit the solenoid holding circuit.

An object is to provide electrical control devices of the type stated in which the solenoid is provided with a holding circuit Which is completed when the relay contact arm engages one stationary contact and is opened when the relay contact arm engages the other stationary contact, whereby the open or closed condition of the load circuit contacts of the solenoid depends upon the last prior closure of the relay contacts.

A further object is to provide an instrument type relay having high and low magnetic contacts, and a solenoid controlled thereby, the armature of the solenoid also being utilized in a mechanical manner for resetting one set of magnetic contacts as the solenoid is energized and for resetting the other set of magnetic contacts as the solenoid is subsequently deenergized, thus eliminating the need for the power relay previously employed to control the load circuit.

These and other objects and advantages will become more apparent from the detailed description and drawings of two preferred embodiments which follow.

Fig. 1 is a schematic view of one embodiment, wherein the instrument is reset in one direction only by the solenoid, while Fig. 2 is a similar view of a second embodiment where the instrument is reset in both directions of motion of the moving system.

Referring now to Fig. 1, the sensitive relay is shown as an electrical measuring instrument 2 having a moving coil I that carries a contact arm 2 on which a small, soft iron rider 3 is fixed. The rider 3 constitutes the moving contact member of the instrument relay and is cooperative with a pair of fixed contacts 4 and 5. Contact member 4 is in the form of a small permanent magnet while the contact 5 is non-magnetic. The coil I may be connected for example across a control device (not shown) such as a thermocouple, photoelectric cell or some other electric device having a very small but variable current output upon which the control is based. The coil i is pivotally supported in the magnetic field set up by a permanent magnet of which only the .poles E, 6 have been shown in the drawing. The coil may turn either clockwise or counterclockwise with increasing current, but, for convenience of description, it will be assumed that the construction is such that the coil turns clockwise with increasing current. Hence as current through 0011 I increases, the contact arm 2 will move clockwise from the low contact 4 towards the high contact 5.

Since contact 4 is a small permanent magnet, a pusher arm or bell-crank lever 1 is provided for resetting the relay when the rider 3 of contact arm 2 has moved into engagement with the contact 4. The lever is mounted on a pivot 8 and has an outer end 9 for engaging the contact arm 2 to separate the contacts 3, '4 upon rocking movement of the lever 7 clockwise against the force exerted by a restoring spring ID. A solenoid H, comprising a winding I2 and armature I3, is located beneath the tail 1 of the resetting lever I for actuating the same.

The solenoid armature l3 actuates a holding circuit switch l4 and a load circuit switch l5 of a controlled device having a higher power requirement than can be handled directly by the contacts of the instrument relay. The energizing circuit for the solenoid ll includes a lead l6 connecting magnetic contact 4 to a source of direct current, indicated by conventional polarity symbols, a lead ll from the contact arm 2 to the winding [2, and a lead 18 and currentlimiting resistor 19 betweenthe other end of the winding I2 and the current source. The holding circuit switch [4 is shunted across the leads I6, I! and the non-magnetic contact 5 is con nected to the lead 18 by a lead 20.

Assuming, as stated above, that magnetic contact 4 is the low contact, the contact arm 2 will move counterclockwise as current through coil I decreases with a change in the magnitude of the measured quantity, and the soft iron rider 3 3 will enter the magnetic field of the contact 4 when the measured quantity reaches one limit of the control range. The rider 3 is then drawn quickly to the magnetic contact 4 and strikes it with sufiicient force to establish a good electrical contact, thereby completing the energizing circuit for the solenoid winding l2. Armature [3 then pulls in to close the holding circuit switch l4 and the load circuit switch l5, and to rock the resetting lever 1 to separate the moving contact 3 from the magnetic contact 4. Obviously, the load circuit switch l may be of the normally closed type when the design requirements are such that the load circuit should'be" opened when the measured quantity reaches the critical value at which contacts 3, 4 engage. The solenoid remains energized after the separation ofl the contacts3, 4 as the holding circuit switch is connected in parallel with those contacts. held away from the contact 4 by the resetting lever 1 and armature l3", and this condition of the several'cir'cui't elements is-maintained until the magnitude of the measuredquantityreaches its other critical limit at which the increasing current through coillcarries the'con-taet arm 2 clockwisete engagethecontact 3 with the stationary contact 5 This contact engagement completes a shunt "circuit around the solenoid winding I2, through the leads 'H- and and the solenoid armature |3-drops out to open the holding circuit and to reverse thecondition of the loadcircuit switch l-5. The continued en'- gagement or repeated engagements, of the contacts 3-, 5 will not result in a change inthe load circuit conditions, and the contact arm 2 must move counterclockwise with decreasing current through coil: I to perm-it engagement of contacts 3-, 4- to-efiect the nextchangeinthe adjustment of the loadcircuit-switch I52 Inthe-embodiment-which is illustrated in Fig, 2, those elements whichare or maybe substantially identical with corresponding elementsofthe Fig. 1 construction are identifiedby corresponding but primedreference numerals; The high contact 5 is a magnetic contactand the solenoid actuating resetting systen i includes two pusher arms or 'bell-cr ank levers 25, 26 on pivots 21, 28 for en'- gag-ing the contact arm 2" toseparate the soft-iron rider contact? from the stationary: magnetic contacts 4', 5" respectively;- The resetting levers 25,. 26. are biased towards inoperative positions out. of the: pathofi movement or the contact arm -2. by springs 28, andtthey-arealternately moved into operative positionshy a bar: 30 on the" upper end of th'e'solenoid'. armature l3, the tall of the lever. 25 being beneath the cross-bar and the" tail 2.6 of. the lever 23 being. above the same.

As illustrated, the solenoid. winding 1 2 is not energized andiaspring3l has forced the armature I31 and bar 30. downwardly, thereby rocking the resettinglever ZE-clockwisetdproject its outer end into the path of the contact: arm- 2 Upon energization of the solenoid winding I2, the armature-J3" isliitedan'd carries the bar 30 upwardly to release the resetting lever 25 and to rock the resetting lever 2 6 counterclockwise to project into the path of the contact arm 2".

The current source for actuating the solenoid H is indicated by the conductors 32', 33 from a schematically indicated alternating current generator, and the current source may conveniently The contact 3 is 5, rider 3' and contact arm 2', jumper H from contact arm 2 to the solenoid winding l2, and return connection 35 from the winding to the other power conductor 33. The holding switch 54 for the solenoid winding [2 is connected in parallel with contacts 3', 5' by a lead 36 to the jumper l1 and a lead 31 to the power conductor 32. A current-limiting resistor l9 and lead 38 connect the-magnetic contact 4' to the power conductor 33. Inspection of the described circuit connections will show that an engagement of relay contacts 3', 4 closes a shunt circuit around the solenoid winding 12', i. e. returns the holding circuit lead 3fi-tothe power conductor 33 through the jumper IT", contact arm 2' and contacts 3, 4', current-limitingresistor l9, and lead 38.

Assuming that the moving coil l is so wound and connected to the control element, not shown,

be" the customary light'and'powercircuit of about the power conductor-32' to the magnetic contact that" increasing current moves the contact arm 2' clockwise towards the contact 5, the several movable parts' of the Fig; 2 apparatus are shown in the positions whichthey' occupy after the current had dropped-toe; value-which resulted in a closure of the relay contacts 3 4 The next closure willbe of contacts 3* and 5' when the current through coil I increases to-the upper limit of the contror range. The energizing circuitof solenoid H willbe completed by that closure of contacts 3', 5 and: the solenoid armature will. lift-to close the holding switclr- I 2 and, as illustrated, the load circuit switch l5. As explainedwith respect'to't-he Fig; I apparatus, the switch [5 could beconstructed to open by the lifting of armature 3. The resetting lever 2-6 is' rocked counterclockwise by bar 30 when the solenoid armature pulls in; and the outer end of lever 26 engages the contact arm- 2 temove the-rider contact 3 a short distance from the magnetic contact 5'. The resetting lever 26 remains in this actuated position solong as the solenoid: winding I2 is energizedthrough the holding circuit switch [4. The next operation of: the relay takes place when the currentthrough coil l drops-tea preselected low value at which contacts-3 4- engage to complet'e'the' shunt circuitaround the solenoid winding I 2. The armature I3'' and bar 30 are then forced downward by thespring: 3 L, thereby opening the holding switch 14- and: loadswitch- Hi. This movement'oithe bar 39 rocks: theresetting lever 25- to separate the contacts- 3 4', and to release the high resetting lever 26 to permit its clockwise: movement into inoperative position by it'sspring 29';- This completes: one cycle of operati'onand the several moving. parts again assunie the positions shown in Fig. 2. wher'rthecurrent'in coil? li' has. increased: somewhat above the low control value at which relay contacts 3',

4 engaged. I

The describedembodiments of the invention (liner in that, both instrument'- type relays are similarly designed: and. connected to. their control elements; the resetting and load switch solenoid is energized? at opposite; limits of: the controlirange of"currentinputsltothe' relay coil Ii or IL. As stated above, it' has been assumed for purpose of description that the relaycontact arms move clockwise with increasing current through the relay coil I or i Identical control operations may of course be obtained by an appropriate reversal of circuit connections when the design is such that the contact armsmove counterclockwise with increasing current;-

In conclusion, it will be evident that while the load switches in Figs. 1i'and?2 have been'illustr'ated as being of the single pole, single-throw type, other types of load switches such as for example a double-pole, double-throw type could be substituted depending upon the particular application made of the relay. Furthermore while the relay in Fig. 1 is illustrated as being powered by direct current and the relay in Fig. 2 by alternating current, it will be evident that both relays will work on either direct current or alternating current. Other minor changes in the illustrated construction may likewise occur to those familar with the design and construction of magnetic contact relays without departing from the spirit and scope of the invention as defined in the appended claims.

I claim:

1. In an instrument type relay for controlling a load circuit in accordance with variation in a control current between predetermined upper and lower limits, an instrument having a moving system displaceable in accordance with the magnitude of the control current, a contact carried by the moving system of said instrument and movable between a pair of spaced stationary contacts, said movable contact and said stationary contacts being magnetically attractive to assure firm engagement therebetween, a pair of pusher arms for separating said movable contact from each of said stationary contacts, a solenoid energized by engagement between said movable contact and one of said stationary contacts, said solenoid hav- 3 ing an armature movable upon energization thereof to actuate one of said pusher arms to separate said contacts and close a solenoid holding circuit, and a shunt circuit for said solenoid holding circuit completed upon engagement between said movable contact and the other stationary contact to effect deenergization of said solenoid and reverse movement of said armature to actuate the other pusher arm to separate the contacts last engaged.

2. In an instrument type relay for controlling a load circuit in accordance with variation in a control current between predetermined upper and lower limits, an instrument having a moving system displaceable in accordance with the magnitude of the control current, a contact carried by the moving system of said instrument and movable between a pair of spaced stationary contacts, said movable contact and said stationary contacts being magnetically attractive to assure firm engagement therebetween, a solenoid having an armature, an energizing circuit for said solenoid completed upon engagement between said movable contact and one of said stationary contacts, a holding circuit for said solenoid completed upon energization of said solenoid, a shunting circuit for said holding circuit completed upon engagement between said movable contact and the other stationary contact, a pair of pusher arms for separating said movable contact from said stationary contacts respectively, and means linking said arms for operation by said armature to reset one of said arms upon energization of said solenoid and to reset the other arm upon deenergization of said solenoid.

3. In an instrument type device for controlling a load circuit in accordance with variation in a control current between predetermined upper and lower limits, an instrument having a moving system clisplaceable in accordance with the magnitude of the control current, a contact carried by the moving system of said instrument and movable between a pair of spaced stationary contacts, said contacts being magnetically attractive to assure firm engagement therebetween, a pair of pusher arms for resetting said movable contact from each of said stationary contacts, means actuating said pusher arms to alternately move each to a contact reset position, a solenoid having a holding circuit including a switch actuated by the solenoid armature, an energizing circuit for said solenoid completed upon engagement between said movable contact and one of said stationary contacts, the armature being actuated by said solenoid upon energization thereof to actuate said pusher arm actuatingmeans to reset the instrument contacts whose engagement efiected energization of said solenoid, and a shunting circuit for said solenoid completed upon engagement between said movable contact and the other stationary contact, whereby said solenoid is deenergized and said last pair of contacts are reset.

4. In an instrument type relay for controlling a load circuit in accordance with Variation in a control current between predetermined upper and lower limits, an instrument having a moving system displaceable in accordance with the magnitude of the control current, a contact carried by the moving system of said instrument and movable between a pair of spaced stationary contacts, said movable contact and said stationary contacts being magnetically attractive to assure firm engagement therebetween, a pair of pusher arms for separating said movable contact from each of said stationary contacts, a solenoid energized by engagement between said movable contact and one of said stationary contacts, said solenoid having an armature movable upon energization thereof to effect movement of one of said pusher arms to separate said contacts and close a solenoid holding circuit, and a shunt circuit for said solenoid holding circuit completed upon engagement between said movable contact and the other stationary contact to effect deenergization of said solenoid and reverse movement of said armature to effect movement of the other pusher arm to separate the contacts last engaged.

RAYMOND T. PIERCE.

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

UNITED STATES PATENTS Number Name Date 2,014,385 Lamb Sept. 17, 1935 2,014,386 Lamb Sept. 17, 1935 2,189,846 Valtat Feb. 13, 1940

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