US3418537A - Relay with chatter preventing shunting circuit - Google Patents

Description

Dec. 24, 1968 M. A. TABET RELAY WITH CHATTER PREVENTING SHUNTING CIRCUIT Filed March 9. 1966 4 TE Fl 6. 2 /9 "'"IO "2L? LOAD 28 29 J 27% k 55 w FIG. 3

Ma k I7LL/ 32 3/ M 2/ x LOAD I INVENTOR MICHAEL A. 74857 ATTORNEY United States Patent 3,418,537 RELAY WITH CHATTER PREVENTING SHUNTING CIRCUIT Michael A. Tahet, 1336 Ballentine Blvd., Norfolk, Va. 23504 Filed Mar. 9, 1966, Ser. No. 533,072 2 Claims. (Cl. 317123) ABSTRACT OF THE DISCLOSURE An energy-absorbing element in parallel circuit relationship with a relay. The energy-absorbing element is taken out of the circuit by a first set of contacts actuated upon initial energizaiion of the relay. Upon the elimination of the shunting energy-absorbing element in the circuit a load set of contacts are actuated.

The present invention relates to a magnetically actuated relay equipped with contacts for opening and closing a load circuit and the invention more specifically pertains to control means in combination with such a relay for preventing chatering of the contacts during opening and closing of the load circuit in response to gradual changes in the voltage applied to the operating coil of the relay.

In operation of such a relay and when there is a relatively slow increase in the voltage applied across the operating coil there is a gradual development of flux and eventually the armature is moved from its inactive position but because of the slow rise in voltage the armature is not shifted to its fully actuated position and there is chattering or fluttering of the contacts. A similar condition develops when voltage impressed across the operating coil slowly decreases because the flux does not collapse abruptly. Chattering of the contacts is particularly pronounced when the relay is operated with alternating current. Vibration or chattering of the contacts in making or breaking a load circuit causes deterioration of the contacts and often provides unsatisfactory operation of equipment forming a part of the load circuit.

It is an object of the present invention to provide means for shunting some of the energy from the operating coil of a relay to prevent premature movement of the armature to thereby provide an additional period of time for a voltage level to be attained which will develop sufiicient current through the operating coil of the relay before the armature is moved from its inactive position and to prO- vide for rendering the shunt inoperative with the result that all of the energy is then applied to the operating coil whereby the armature is abruptly shifted to its full actuated position to provide for snap operation of the contacts which control a load circuit.

Another object of the invention is to provide an energy-absorbing element in parallel circuit relationship with the operating coil of a relay so that some current is diverted from the operating coil while the voltage applied thereto slowly increases in value including means to interrupt the parallel circuit upon initial movement of the armature from its inactive position whereby the armature then abruptly moves to its fully actuated position to positively close or open the load controlling contacts with the assembly insuring re-establishment of the energy-absorbing circuit as the armature initiates its return to the inactive position.

A more specific object of the invention is to provide an energy-absorbing element such as resistance, condenser, or inductance in parallel circuit relationship with the operating coil of a relay so that when the armature first moves from its inactive position contacts in the parallel circuit disconnect the energy-absorbing element whereby the entire voltage which is then available will then be applied across the operating coil of the relay for shifting the armature to its full actuated position with the unit so arranged that energy-absorbing element is placed in parallel relationship with the operating coil upon initial movement of the armature from its fully actuate-d position.

Other objects and features of the invention will be appreciated and become apparent to those skilled in the art to which the invention pertains as the present disclosure proceeds and upon consideration of the accompanying drawing taken in conjunction with the following detailed description wherein an embodiment of the invention is disclosed.

In the drawing:

FIG. 1 is a fragmentary side elevation view of elements of a relay forming a component of the invention.

FIG. 2 is a circuit diagram of a combination which embodies the invention and showing relay elements of FIG. 1.

FIG. 3 is a view similar to FIG. 2 wherein the contacts of the relay for controlling the load circuit are normally open.

The invention pertains to means for controlling the operation of a relay which may take various forms and in the embodiment shown in the drawing the operating coil is indicated at 10. An electrical source of generally fixed voltage is indicated at 11. The relay is equipped with an armature 12 which is in an inactive position when the operating coil 10 is deenergized. A relatively rigid bar 14 is mounted in any suitable insulated manner on the relay frame. A contact 17 carried by the bar 14 is adapted for cooperation with a contact 18 carried by a resilient blade 19 which is mounted in an insulated relationship with respect to the relay frame. The contacts 17 and 18 are for controlling a load circuit which extends from one side of the source 11 through a conductor 21, a conductor 22, the contacts 17 and 18, the blade 19 and to the other side of the electrical source.

A unit embodying the invention has particular utility when the electrical source has a substantially fixed voltage and control of the relay is carried out by voltage varying means such as an adjustable resistor or impedance 26 which varies slowly whereby its ohmic or impedance value is altered by small increments over a protracted period. The voltage varying means 26 may take the form of a photoelectrical element the resistance of which decreases when light falling thereon increases and the resistance of which increases when light falling on the photoelectric element decreases.

A unit for controlling a load circuit and exhibiting the invention includes a second set of normally closed contacts 27 and 28. The contact 27 is carried by the resilient blade 19 while the contact 28 is carried by another spring type blade 29 mounted in an insulated manner on the relay frame. A stud 31 formed of insulating material is arranged to be shifted by the armature 12 and a nose portion 33 on the stud engages the blade 29 to move the contact 28 from engagement with the contact 27 upon initial movement of the armature from its inactive position. During this initial movement of the stud the normally closed contacts 17 and 18 remain in engagement.

A circuit shunts the operating coil 10 and includes an energy-absorbing element 36 such as a resistor. The energy-absorbing element may take the form of a condenser or inductance when the operating supply is alternating current. The shunt circuit extends from one side of the source 11 through the normally closed contacts 27 and 28, the blade 29 and the energy-absorbing element 36 to the other terminal of the operating coil 10. The energy-absorbing element 36 is thus in parallel circuit relationship with the operating coil 10. The impedance of the coil in relation to resistance or impedance of the energy-absorbing element 36 is such that a major portion of the current flows through the operating coil 10. In one satisfactory embodiment approximately one-fourth of the current flowing in the circuit bypasses the operating coil 10.

When the armature is in the inactive position and upon the occurrence of a slow change of the voltage varying means current flows through the operating coil 10 and a minor portion of the current flows through the energyabsorbing element 36 which is then in parallel circuit relationship with the operating coil 10. If the voltage varying means is an adjustable resistor and as its ohmic value is slowly decreased sufiicient flux is developed by the coil 10 to move the armature 12 from its inactive position. Such initial movement of the armature causes the nose portion 33 of the stud 31 to move the contact 28 from engagement with the contact 27. The bypass circuit is thereby interrupted and all of the current then flows through the operating coil 10 and the armature 12 shifted abruptly to its fully actuated position. During such movement of the armature a shoulder 32 on the stud 31 engages the blade 19 and moves the contact 18 from engagement with the contact 17. Thus the contacts controlling the load circuit are opened with abrupt action and chattering of the contacts 17 and 18 is avoided.

The unit also serves to prevent fluttering of the contacts during closing of the load circuit. As the voltage applied across the operating coil 10 slowly decreases the flux decreases but does not collapse. Eventually the armature 12 retreats slightly from its fully actuated position and the contact 28 then engages the contact 27. Such action places the energy-absorbing element 36 in parallel circuit relationship with the operating coil 10 and a minor portion of the current then flows through the shunt circuit. When the contacts 27 and 28 close there is a pronounced decrease in the flux developed by the coil 10 whereby the armature 12 abruptly moves to its inactive position by action of the resilient blade 29 and the blade 19 moves the contact 18, without chattering or fluttering into engagement with the contact 17 to energize the load circuit.

The unit shown and described in connection with FIGS. 1 and 2 has particular utility when used on alternating current for controlling the energization of a load such as a street lamp or lamps and when the voltage varying means 26 is in the form of a photoelectric element of the broad area cadmium sulphide type. Such a photoelectrical element is commercially available but has a limited energy handling capacity and in a range below three hundred milliwatts. The spring pressures of the blades 19 and 29 are then of low value of about sixty grams when the supply source 11 is in the one hundred ten voltage range. Under such conditions the chattering of the contacts 17 and 18 is pronounced because of the slow and protracted changes in the resistance of the photoelectric cell as a consequence of gradual changes in the natural light Which occurs in the morning and evening hours. When the load circuit or lamp is energized the natural light falling on the photoelectric element increases slowly in the morning so that the current flowing through the operating coil 10 increases at a slow rate and over an extended period. Eventually the armature 12 moves slightly from its inactive position. The nose 33 of the stud 31 then moves the contact 28 from engagement with the contact 27 whereby the energy-absorbing element 36 is no longer in parallel circuit relationship with the operating coil 10. The armature 12 then moves abruptly to its fully actuated position and the shoulder 32 on the stud 31 moves the contact 18 in a positive manner from engagement with the contact 17. The lamp circuit is thus interrupted and the lamp is deenergized without fluttering or chattering of the contacts which control the load circuit.

Such desired results are attained in the evening when the light falling on the photoelcctrical element decreases which provides an increase in the resistance 26. The armature in its initial movement from the fully actuated position allows the blade 29 to move the contact 28 into engagement with the contact 27. The shunt circuit then diverts current from the operating coil 10 whereby the armature 12 abruptly moves to its inactive position. The load contacts 17 and 18 are thereby closed without fluttering action to energize the load circuit.

A unit embodying the invention may include other relays such as the type shown in FIG. 3 wherein the contacts 27 and 28 are normally closed but the contacts 17a and 18a for controlling the load circuit are normally open. The resilient blade supporting the movable contacts 17a is adapted to be engaged by the shoulder 32 on the stud 31 for closing the contacts 17a and 18a after the contact 28 has been moved from engagement with the contact 27. The contacts 27 and 28 close upon initial movement of the armature from its fully actuated position. The armature then moves abruptly to its inactive position whereby the contact 17a moves with positive action from the contact 18a.

While the invention has been described with regard to one general type of relay wherein the contacts are supported by resilient blades which serve to return the armature 12 to its inactive position changes may be made in the structural features of the relay. Other alternations may be made in the elements as well as the overall assembly without departing from the spirit and scope of the invention as set forth in the appended claims.

What I claim and desire to secure by Letters Patent is:

1. An electrical unit for opening and closing a load circuit comprising, a relay having an operating coil and an armature and first contacts engaged and disengaged upon movements of the armature for controlling a load circuit, an electrical source and means for varying the voltage thereof, means applying said variable voltage to said operating coil, a circuit including an energy-absorbing element therein and normally closed second contacts in parallel circuit relationship with said operating coil shunting a portion of the current developed by said variable voltage from the operating coil, and means actuated by initial movement of the armature from its inactive position opening said second contacts whereby all of the current developed by said variable voltage is applied to said operating coil to abruptly actuate the first contacts.

2. An electrical unit for opening and closing a load circuit according to claim 1 wherein the means actuated by initial movement of the armature from its inactive position is constructed and arranged to provide for closing of the second contacts upon initial movement of the armature from its fully actuated position whereby the parallel circuit and the energy-absorbing element divert current from the operating coil to provide for abrupt movement of the armature to its inactive position.

References Cited UNITED STATES PATENTS 1,242,763 10/1917 Bossu 317123 1,246,687 11/1917 Wells 317123 LEE T. HIX, Primary Examiner.

J. A. SILVERMAN, Assistant Examiner.

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