US2864923A - Electric relay - Google Patents

Description

Dec. 16, 1958 c. A. MATHEWS 2,864,923

ELECTRIC RELAY Filed May 17, 1957 F/ F/ .2. K I 44 g Inventor:

Chfies A. athews, b9 His t'borneg.

United States Pate 1' ELECTRIC RELAY Charles A. Mathews, Springfield, Pa., assignor to General Electric Company, a corporation of New York Application May 17, 1957, Serial No. 659,797

Claims. (Cl. 200-166) This invention relates to electric relays, and more particularly to the structure of an electromagnetic-induction type relay wherein contact bounce is minimized or eliminated.

When an electromagnetic relay is actuated, a movable contact is driven by magnetic forces into engagement with a cooperating fixed contact. Usually the movable contact is moving with significant velocity when it strikes the fixed contact, and the movable contact will tend to rebound or bounce away from the fixed contact with undesirable effects. For example, the bouncing contacts may draw an electric are which rapidly pits and deteriorates the contacts. Many dilferent solutions to this problem have been oflered, the typical solution utilizing energy storing means, for example, a leaf spring, to cushion the force with which the movable contact strikes the fixed contact. But most energy storing means presently in use are not entirely satisfactory, since they return the energy stored after the magnetic driving forces are reduced or removed thereby causing the movable contact to kickoff or rebound from the fixed contact. In other words, the action of the energy storing means in cushioning the movable contact and preventing initial contact bounce is directly reflected by the reaction with which the stored energy is returned upon removal of the contact closing force.

The disadvantages of the above described typical arrangement are particularly evident in a high-speed relay having double-throw contacts, that is, a relay having a single moving contact disposed between a pair of spaced apart fixed contacts, the moving contact being biased normally to engage one of the fixed contacts (normally closed) and being moved by magnetic forces into engagement with the other fixed contact (normally open). in such a relay it may be highly undesirable to have the moving contact bounce back to its normally closed positron.

Accordingly, it is a general object of this invention to provide an electric relay having improved means for preventing contact bounce.

Another object of the invention is the provision, for an electric relay having a moving contact and a fixed contact, of means for limiting the impact with which the moving contact strikes the fixed contact.

Still another object is to provide an electric relay having a spring clutch which will limit the torque transmitted to a fixed contact when the cooperating movable contact is driven in a predetermined direction and which will transmit unlimited torque to another fixed contact when the movable contact is driven in the opposite direction.

In carrying out my invention in one form, an electric relay having a stationary contact, a cooperating movable tact is carried into engagement with the stationary contact. But when the movable and stationary contacts are engaged, the spring clutch means is arranged to slip with respect to the driven member thereby transmitting only a limited amount of torque to said driven member. However, when the driving member is moving in the opposite direction, the spring clutch means will transmit unlimited torque to the driven member.

My invention will be better understood and further objects and advantages will be apparent from the following description taken in conjunction with the accompanying drawing in which: n

Fig. .1 is an exploded perspective view of the movable contact, the driven member, the driving member, and the spring clutch means of an electric relay constructed in accordance with my invention;

Fig. 2 is an elevational view of the electric relay;

Fig. 3 is a plan view of the electric relay; and

Fig. 4 is a section taken along lines 4-4 of Fig. 3 with the driven member being rotated in a clockwise direction with respect to the position in which it is shown in Fig. 3. i

Referring now to Fig. 1, the electric relay that has been illustrated for the purpose of describing the present invention comprises a driving member 11, a driven member 12, and a movable contact 13 mounted on the driven member. The driving member 11 is a vertically disposed rotatable shaft having its lower end located centrally Within a frame or box 14 shown in Figs. 2 and 3. The

lower end of driving member 11, which is supported for rotation about its axis in opposite directions by a suitable bearing not shown, is connected to an induction cup or disk not shown. The induction cup or disk is disposed contact mounted on a driven member, and a driving member-is providedv with spring clutch means disposed in a manner to interconnect the driven and driving members. When the driving member is moving in a predetermined direction, the spring clutch means causes the driven member to move correspondingly whereby the movable conin magnetic fields established by the energization of various windings, not shown, to provide a source of torque which may cause shaft 11 to rotate in either direction. It will be assumed that torque set up under normal conditions tends to rotate the driving member 11 counterclockwise as viewed in Figs. 1 and 3, and that torque set up under operating conditions t nds to drive the driving member clockwise.

The upper end of driving member 11 comprises a reduced-diameter portion 15 the extremity of which is threaded, as is clearly shown in Figs. 1 and 4. The shoulder formed by the reduction in diameter in member -11 has been identified by the reference number 16. A

bushing is provided in the tip of driving member 11 to form a pivotal bearing with a fixed pin 17 which, as can be seen in Fig. 2, is disposed in a bracket 18 mounted on frame 14 by means of a pair of spaced apart raised supports 19a and 19b.

The driven member 12 comprises a generally spoolshaped contact carrier disposed adjacent to and in axial alignment with driving member 11. Member 12 preferably is made of electrical insulating material, and it is provided with a pair of flanges 20 and 21 and an axial.

opening for loosely receiving the reduced portion 15 of driving member 11. A cylindrical portion 22 projecting from the lower flange 21 of the driven member rests on shoulder 16 of the driving member in the manner clearly shown in Fig. 4. The driven member 12 also'includes a web 23 extending between flanges 20 and 21, as can be seen in Fig. 4. V

The movable contact 13 comprises a current conduct ing pin-like element 24 affixed to a flat washer 25 as is shown in Fig. 1. The washer 25 fits over the cylindrical portion 22 and under the lower flange 21 of driven member 12 where his mounted by means of a pair of rivets 26a and 2612 or the like. When mounted in this manner, pin 24 extends in'an axial direction through lower flange 21 and fits snugly into a cooperating recess 27 in-the lower side of the upper flange 20. See Figs. 1 and 4,

The movable contact 13 also includes a tab 28 extending in an axial direction below washer 25. As is indicated in Figs. 1 and 4, the tab 28 is secured to the inner end of a coil spring 29 whose outer end is secured to a cooperating projection 30 of an adjustable ring 31. The adjustable ring 31 is clamped firmly but rotatably to a supporting bracket 32 by means of a collar 33 as shown. Bracket 32 is securely mounted on frame 14 by means of a pair of ears 34a and 34b which may be fastened to appropriate raised supports 35 only one of which is shown in Fig. 3.

The coil spring 29 provides a bias that urges the movable, contact 13 and hence the driven member 12 in a counterclockwise direction on driving member 11 as viewed in Figs. 1 and 3. By applying sufficient manual force to rotate the adjustable ring 31 with respect to bracket32, the tension of coil spring 29 may be changed to vary correspondingly the amount of bias exerted on driven member 12. Coil spring 29 also provides an electric connection betweenthe movable contact .13 and the supports 35 which can serve as terminals for suitable connectors associated with remote electric circuits not shown.

The top surface of the upper flange 20 of the rotatable driven member 12, which surface lies generally-perpendicular to the axis of rotation, comprises a plurality of gently sloping inclined portions 36 defined by four abruptly disposed vertical portions 37 as is clearly shown in Fig. 1. Each of the vertical portions 37 is radially orientedon-the surface, i. e., itdefines a radius of the generally disk-shaped upper face of the driven member 12. Thus, four angularly spaced notches are formed at approximately 90 degree intervals in the upper face of member 12, one side (37) of each notch being disposed generallyperpendicular to the plane of the face and the other side (36) of each notch providing a relatively gently sloping incline.

In accordance with my invention, the driving member 11 and the driven member 12 are interconnected by means of a torque transmitting coupling member 38 which is designed to provide unidirectionally effective overload slipping clutch action. As can be clearly seen in Fig. 1, member 38 comprises a springclutch having a washer-shaped body portion 39 andhaving three stifliy resilient, generally tangential-oriented elements or fingers 40 disposed along its circumference.

Located in the middle of the body portion 39 is a non-circular hole through which a correspondingly configured neck 41 ofan adjustable supporting collar 42 is snugly inserted. The collar 42, which is tapped throughout its axial length, is provided with a hexagonal head 43, as is clearly seen in Fig. l. The supporting collar 42 is threaded onto the upper extremity of the reduced portion 15 of driving member 11 and, as shown in Fig. 4, is securely fixed to the member11 in a selectable axial position by means of a lock nut 43. Thus, the spring clutch 38 is disposed in a plane generally perpendicular to the axis of the driving member 11, and the clutch is bi-directionally movable in accordance with rotation of the driving member.

The spring clutch or coupling member 38 is captured between head 43 of supporting collar 42 and the adjacent upper face of the driven member 12. See Figs. 2 and 4. The resilient elements or fingers 40 project at acute angles from the plane of the spring clutch for slidable engagement with the adjacent face of the driven member The cooperating parts are arranged so that fingers 40 may inactively slide over the inclined portions 3.6-.of the adjacent face when the driving member 11 is rotating clockwise as, viewed in the drawing and so that thesefinge'rs may abut the vertical portions 37 of said face, when the driving member is rotating counterclockwise.. The fingers 40 apply torque transmitting pressure to drivenmember 12, and the amount of pressure being applied is determined by the axial position of the adjustable supporting collar 42. Of course, the frictional forces which resist slippage between spring clutch 38 and the inclined surfaces 36 are directly related to the amount of pressure being applied.

Referring now to Figs. 2 and 3, a pair of spaced apart fixed or stationary contact elements identified generally by the reference numbers 45 and 46 are disposed in co operating relationship with the movable contact 13. The movable contact element 24 is located intermediate the fixed contacts 45 and 46 and is respectively engageable therewith to determine opposite limits of reciprocal movement of the driven member 12. Contact 45 stops counter clockwise rotation of member 12 thereby establishing the normally closed position of the movable contact 13, while contact 46 stops clockwise rotation of member 12 thereby establishing the operated position of the movable contact.

As can be seen most clearly in Fig. 3, each of the fixed contacts 45 and 46 comprises a bracket 47 supported by an L-shaped clip 48 which is securely mounted on frame 14. A leaf spring 49 of current conducting. resilient material is fastened at one end to bracket 47, and this spring carries at its other end a small pin-like current conducting member 50 which extends horizontally into the path of movement of the vertical pin 24 of movable contact 13. A disk-shaped member 51 is also aifixed to bracket 47 to form a back stop for member 50 as shown. With the leaf spring 49 in an undeflccted state, member 50 is spaced apart from the face of the associated back stop 51.

The movable contact 13 is urged in a counterclockwise direction by bias spring 29. As contact 13 moves in the counterclockwise direction toward fixed contact 45, pin 24 engages member 50 thereby deflecting the leaf spring 49 associated with contact 45. The member 50 now travels with pin 24 for a short distance until it is seated firmly against the back stop 51. In order to deflect spring 49, some of the energy with which the moving pin 24 strikes member 50 must be utilized, and thus less energy is available when the combination of pin 24 and member 50 reach the immovable back stop 51. In this manner the impact of the moving parts and the fixed parts is reduced, and contact bounce is correspondingly reduced.

The action described above also takes place when the movable contact 13 moves in a clockwise direction to engage fixed contact 46. But shortly before pin 24 first touches the member 50 associated with contact 46, the clockwise rotation of movable contact 13. is resisted by another coil spring 52 which has been illustrated in Figs. 3 and 4. The coil spring 52 is disposed on a spool 53 which includes an axially extended cylindrical pinion 54 protruding through a corresponding opening in a mounting plate 55. By means of a spring washer 56, a flat washer 57 and a retaining clip 58, spool 53 is firmly but rotatably secured to the mounting plate 55. Plate is affixed to frame 14 by means of a pair of spaced apart raised supports shown as 59a and 59b in Fig. 3.

The outer end 60 of coil spring 52 is bent across a pin 61 projecting from plate 55, as is shown in Figs. 3 and 4. Pin 61 prevents spring 52 from unwinding from its outer end. End 60 extends into the space between flanges 20, and 21 of the driven member 12 where it lies in the path of movement of the web 23. Thus, as the movable contact 13 is carried by member 12 in a clock- Wise direction, and before pin 24 first engages the member 50 associated with the fixed contact 46, web 23 comes into contact with the end 60 of coil spring 52. Further clockwise movement of contact 13 and member 12 causes web 23 to push against end 60 in opposition to a force exerted by coil spring 52. This added resistance to clockwise rotation may be used to determine the pick-up level of the magnetic forces which propel the driving member 11. The amount of force that is necessary to overcome the bias provided by coil spring 52 and thus defiect theend 60 may be adjusted by applying sufficient manual force to turn the pinion 54 of spool 53 thereby changing the initial tension of the coil spring 52.

From the foregoing detailed description of the structure of the electric relay incorporating my invention, itsmode of operation may now be readily followed. Although not essential to a complete understanding of the mechanical operation described hereinafter, it may be helpful first to establish certain premises in regard to normal and operating electrical conditions which determine the amount and direction of the torque in the bidirectionally rotatable driving member 11. It has been mentioned hereinbefore that the torque of driving member 11 is provided in the first instance by the interaction of magnetic fields established by appropriate energization of various windings, not shown, located in box 14. The torque is directly proportional to the vector product of the two basic energizing quantities, and these quantities may be assumed to comprise current and voltage in a circuit (not shown) being protected by the illustrated relay. In other words, torque is proportional to the product of the magnitudes of circuit current and voltage multiplied by a function of the angle between them. This angle between current and voltage is known as the power factor angle of the circuit.

Under normal conditions, a predetermined magnitude of circuit current is flowing at a power factor angle nearly zero, and a predetermined amount of torque in the counterclockwise direction is provided. Operating conditions are caused by a reversal in the direction of circuit current, and the direction of torque reverses accordingly and becomes clockwise. Under extreme operating conditions, such as caused by a circuit fault, the current magnitude increases sharply, but the magnitude of clockwise driving torque may be either less than or much greater than the aforesaid predetermined amount, depending upon the power factor angle. In other words, although the magnitude of circuit current during a fault may be much greater than normal, the magnitude of torque may be less than normal due to a larger power factor angle. Prior to operation, the various relay components are in the respective positions shown in Figs. 2 and 3. When an operating condition develops, and the resulting driving torque is sutficient to overcome the bias of coil spring 29 and the inertia of the moving parts, the driving member 11 will rotate in a clockwise direction from the posi tion shown. The spring clutch 38, which is carried by driving member 11, transmits the driving torque to the driven member 12.

The resilient fingers 40 of spring clutch 38 apply a predetermined amount of torque transmitting pressure to the cooperating inclined surfaces 36 of driven member 12. This predetermined amount of pressure is selected by means of the adjustable supporting collar 42 to ensure that no slippage will occur between the clutch and the driven member while the clutch is rotating in a clockwise direction as long as the opposing forces which are exerted on the driven member comprise only the bias of coil spring 29, the bias of coil spring 52, the inertia of the driven member itself, the friction of the bearing surfaces of the driven member, and the deflection of the leaf spring 49 associated with fixed contact 46. In order to obtain a substantially constant application of the torque transmitting pressure between clutch and driven member, regardless of the relative positions of these two members, I have made the number (3) of fingers 40 different than the number (4) of inclined surfaces 36.

When the driven member 12 has been driven to the limit of its clockwise rotation, the movable contact 13 engages the cooperating fixed contact 46, and further movement of the driven member 12 is prevented. However, the driving member 11 may continue to rotate in the clockwise direction as the spring clutch 38 permits relative movement of the members 11 and 12. Only a limited amount of torque will be transmitted by the spring clutch 38 to the now firmly stopped driven m'ez'nber 12, and any excessive driving torque in member 11 causes the resilient fingers 40 to yield and slide inactively over the gently sloping inclined surfaces 36 of the driven member. Ordinarily the operating conditions are severe, and the movable contact 13 will be traveling with significant velocity when it strikes the cooperating fixed contact 46. But the initial impact is no greater than that attributable to the mass of the driven member 12 and the frictional drag of the spring clutch 38. In other words, the movable contact can expend only a definitely limited amount of energy when striking the fixed contact, the remainder of the driving energy in member 11 being used to overcome the increased frictional losses and to accelerate the driving member 11.

The aforesaid limited amount of torque is selected to be sufficiently low so that the tendency for movable contact 13 to rebound from fixed contact 46 is negligible with this particular amount of torque being transmitted.

I have found that this limited amount of torque is less than the above-mentioned predetermined magnitude of counterclockwise torque developed under normal conditions. Any excessive driving torque is not transmitted to the movable contact in its operated position, and as a result, the tendency for contact 13 to rebound is minimized or completely eliminated regardless of how great the driving torque may be. The continued frictional drag of the slipping clutch in the clockwise direction contributes further to the reduction of contact bounce.

When the operating conditions are removed and the driving torque in member 11 becomes Zero, the driven member 12 will be free to rotate counterclockwise with movable contact 13 in accordance with the various bias elements. The movable contact 13 ordinarily moves relatively slowly while returning to its normal position engaging the fixed contact 45, and there is little tendency to bounce. In addition, the current making duty of the normally closed contacts is usually relatively small, and thus the problem of contact sparking during counterclockwise or resetting movement is negligible.

In a typical relay application, following a relay operation, the circuit conditions will return to normal only after the movable contact 13 has returned to its normally closed position. In other words, there is an intermediate step during which driving torque is zero and the movable contact resets before normal conditions may be resumed. Upon the return of normal conditions, counterclockwise torque is set up in driving member 11, but counterclockwise rotation of this member is prevented for there can be no relative movement of the members 11 and 12. One of the resilient fingers 40 of spring clutch 38 abuts one of the vertical side walls 37 of the notches formed in the upper face of driven member 12, and the driven member 12 is rendered immobile by the engagement of movable contact 13 with cooperating fixed contact 45. Thus, all of the torque of driving member 11 is transmitted to the driven member 12 which is stopped by the fixed contact 45. The reason for the unidirectional design of the clutching arrangement is to avoid continuous slippage and resulting wear during normal conditions, the magnitude of normal torque being sufliciently great to cause slippage if otherwise permitted.

While I have shown and described a preferred form of my invention by way of illustration, many modifications will occur to those skilled in the art. I therefore contemplate by the claims which conclude this specification to cover all such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by United States Letters Patent is:

l. A relay comprising: a stationary contact; a cooperating movable contact; a driven member providing a mounting for said movable contact, said driven member being movable in a predetermined direction to carry said movable contact into engagement with said stationary contact;

assign;

viding a source of torque; and springclutch means inelud:

ing at least one resilienttinger-l ike elementinterconnecting said driven and driving members in amanner to transmit only a limited amount of torque to said' driven member whenever said movable and stationary contacts are engaged and said driving member is moving in a direction corresponding to said predetermined direction, said spring clutch means being arranged to transmit unlimited torque to said driven member when said driving member is moving in the opposite direction.

2. A double-throw relay comprising: a pair of relatively stationary spaced apart contact elements; a driven member reciprocally movable between predetermined limits, said driven member having a contact elementdisposcd intermediate said relatively stationary contact elements an; respectively engageable therewith to determine the predetermined limits of reciprocal movement of said driven member; and a iii-directionally movable driving member disposed adjacent said driven member for providing a source of torque; one of said members including a resilient finger disposed in torque transmitting pressure applying engagement with a cooperating surface of the other member, said resilient finger and cooperating surface being constructed and arranged to permit relative movement of said members when said driving member is moving in one direction and said driven member has been moved in said one direction to the corresponding limit of its movement and to prevent relative movement of said members when said driven member has been moved in the opposite direction to the other limit of its movement.

3. A relay comprising: a rotatable driving member having an axis; a rotatable driven member disposed in axial alignment with said driving member and including a sur face disposed generally perpendicular to said axis, said surface having at least one radial-oriented notch therein; a movable contact mounted on said driven member; a relatively stationary contact disposed in cooperating relationship with said moving contact; a torque transmitting coupling member affixed to said driving member adjacent to the surface of said driven member, said coupling member including at least one generally tangential-oriented resilient projection disposed slidably to engage said surface in torque transmitting pressure applying relationship; and adjustable means associated with the coupling member for determining the amount of torque transmitting pressure applied by said coupling member.

4. In a relay-:- a driven member including a surface having at" least one notch therein, one side of said notch being disposed generally perpendicular to the plane of said surface and the other side of said notch forming a relz tively gently sloping incline; biasing means disposed to urge said driven member in a predetermined direction; a movable contact-mounted on said driven member; a relatively stationary contact disposed to be engaged by said moving contact and to provide a stop for said driven member when said driven member is moved in the direction opposing its bias; a driving member movable in 0;:- posite directions disposed adjacent to said driven member; and a clutching member affixed to said driving member and including at least one resilient finger disposed to engage the surface of said driven member, said finger being arranged to abut the perpendicular side of said notch when said driving member is moving in a direction corresponding to the predetermined direction of said driven I member and to' slide inactively over the inclined side of said notch whenever said driving member is moving in the opposite direction after said movable contact has engaged said stationary contact.

5. A'relay comprising: a bi-directionally rotatable driving member having an axis; a rotatable driven member disposed in axial alignment with said driving member and including a disk-shaped face disposed generally perpendicular to said axis, said face having a plurality of an gularly spaced'notches formed therein; a movable contact mounted on said driven member; a relatively stationary contact disposed in cooperating relationship with said movable contact; and a torque transmitting washer-shaped coupling member aflixed to said drying member in parallel relationship to'the face of said driven member, said coupling member including a plurality of resilient elements circumscribing said axis and projecting at acute angles from the plane of said coupling member for slidnble cngagement withsaid face in torque transmitting pressure applying relationship;

References Cited in the file of this patent UNITED STATES PATENTS 2,098,032, Favre Nov. 2, 1932 2,143,550 Gilbert Jan. 10, 1939 2,400,818 Gallagher May 21, 1946

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