US2385994A - Relay - Google Patents

Description

Oct. 2, 1945. J JOHNSTON 2,385,994

RELAY Filed Nov. 26, 1945 Patented Oct. 2, 1945 RELAY Arthur J. Johnston, Park Ridge, Ill., assignor to C. P. Clare & 00., Chicago, 111., a corporation oi Illinois Application November 26, 1943, Serial No. 511,815

9 Claims.

The present invention relates in general to relays, and the object of the invention is to produce a new and improved relay.

More in particular, the invention relates to relays oi the type in which so-called contact springs are employed to open or close electrical circuits. A well known relay of this type is commonly referred to as a telephone relay. Such relays may have one or more working contact springs, or armature springs, and so-called make contact springs or break contact springs with which the working contact springs cooperate. They find application not only in telephone systems but in various types of selection and control systems.

A defect in telephone relays and other relays in which make or break contact springs are empioyed is what is generally known as contact bounce. To explain what is meant by this term a simple relay having an armature spring and a cooperating make contact spring may be referred to. When the relay is energized the armature is sharply attracted and the working contact spring is moved suddenly into engagement with the make contact spring, striking the latter a sharp blow, which tends to make it vibrate. The vibrations, when they occur, are of relatively high frequency and are highly damped. The extent-to which the vibrations occur depends on the adjustment of the relay and various other factors which need not be gone into. The effect of the vibrations depends on their amplitude, which may be enough to open the circuit, perhaps two or three times, beiore the vibrations die out and the contact becomes solidly closed.

Contact bounce can be detected by means of a cathode ray oscillograph, having a suitable sweep voltage applied to the horizontal deflector plates and using the relay contacts to be tested to apply a direct current voltage to the vertical deflector plates. If no contact bounce takes place the ray will be deflected when the relay is energized and the deflection will be maintained until the relay is deenergized; whereas if contact bounce is present the initial deflection of the my will not be maintained but the ray will make one or more rapid incursions toward the normal line. These rapid inmrruptions in the deflection are caused by high frequency vibrations of the make contact spring which open the circuit.

Contact bounce may also take place at a break contact spring when the relay is denergized and the working contact spring comes into engagement with the break contact spring.

Contact bounce does no particular harm under many circuit conditions. In the case of a relay which simply closes a low current circuit and holds it closed for a few seconds or longer, contact bounce is usually of no appreciable effect and is more or less unobjectionabie. If the same relay is used to start a direct current motor, however, and if contact bounce is present, the motor circuit will be opened at a time when the motor is taking a heavy current and destructive arcing will occur. Another illustration is an impulsing relay, controlled over a line circuit and delivering impulses to the motor magnet of a stepping mechanism. If the impulsing relay operates at a slow speed, the arrangement may operate all right notwithstanding a certain amount of contact bounce, but if the relay is required to operate at high speed, say thirty or more impulses per second, each impulse is oi relatively short duration and the portion of each impulse which may be lost due to contact bounce becomes appreciable and may seriously interfere with the operation of the circuit.

The invention provides a simple and effective means for eliminating contact bounce, comprising a resilient support for the make and break contact springs of a relay. According to the preferred embodiment of the invention, the support consists of a body of soft rubber or equivalent resilient material which bears against the edges of the contact springs near the contact ends thereof and is effective to prevent the springs from vibrating.

The invention will be described more in detail hereinafter, reference being made to the accompanying drawing, in which Fig. 1 is a top or plan view of a relay embodying the invention;

Fig. 2 is a side view of the same; and

Fig. 3 is a partial section on the line 3-3, Fig. 1.

Referring to the drawing, the relay shown therein is for the most part or" known construction, and comprises a magnetic structure including an armature, two working contact springs adapted to be operated by the armature when the relay is energized, and make and break contact springs which cooperate with the two working contact springs, respectively. This arrangement of contact springs provides for closing one circuit and opening another circuit upon energization of the relay. Various other spring combinations may be employed.

The magnetic structure includes the core I 0, winding 6 l, and the heel piece l2, the latter being attached to the core II) by means of a machine screw l3. The armature is indicated at H and has an integrally formed arm i! for operating the working contact springs and two integrally formed ears i6 and I1 by means of which it is pivotally supported on the bracket it. This bracket is secured to the heel piece i2 by means of a washer I9 and screw 20 and has two integrally formed ears 2| and 22 which extend between the ears i6 and ll of the armature I4, as shown clearly in Fig. 1. The pivot rod 23 passes through holes drilled in the ears it and ii and is rotatable in bearings formed in the cars 28 and 22.

The two working contact springs are indicated at 25 and 28. A break contact spring 28 cooperates with the working contact spring 25, while the make contact spring 21 cooperates with the working contact spring 28. These contact springs are clamped to the heel piece E? by means of a rectangular washer 33 and the two screws 3! and 32. The spring assembly also includes a plurality of insulators such as 36 and a stop 35 which is located next to the heel piece.

The shape of the contact springs can be seen clearly in Fig. 1. The working contact springs such as 25 are relatively long and narrow, providing the necessary flexibility; while the make and break contact springs such as 26 are shorter and wider, and generally speaking, are stifier than the working contact springs. The flexibility or stifiness of the springs is, of course, also dependent on the gauge of metal used, which varies with the operating characteristics required. The make and break contact springs such as 26 have side extensions at the ends which project into the path of the working contact springs such as 25. These extensions'carry contacts which cooperate with contacts on the working contact springs.

The working contact springs are tensioned downward, as the relay is seen in Fig. 2. Spring 28 bears against the bushing 30 on the arm 15 of armature i4, and arm it rests against the adjustable stop 35, by means of which the normal position of the armature and spring 28 is determined. The stop 35 and make contact spring 27 are so adjusted that the working contact spring 28 is out of engagement with the make contact spring 27; that is, the contact is open. The working contact spring 25, on the other hand, is in engagement with .the break contact spring 26; that is, the contact is closed. The spring 25 carries a bushing 29, which lies between the springs 25 and 28. The adjustment should be such that this bushing is very nearly in engagement with spring 28, or perhaps in light contact therewith. It is preferable that spring 28 be normally slightly separated from bushing 29 so as to insure that there is no reduction in contact pressure between springs 25 and 25,

The break contact spring 26 and the make contact spring 21 are supported near their ends by an arrangement which will now be described. The reference character 40 indicates a fiat rectangular bracket member'which rests against the heel piece l2 and is secured thereto by a screw 4|. At the end opposite the screw 4| the bracket 40 is provided with a pin or stud 42 which may be secured to the bracket by riveting, as indicated in Fig. 3. The stud 42 supports a cylindrical body of resilient insulating material indicated at 43, which may be a short section of rubber tubing. The tubing should have relatively thick walls and an internal diameter which i somewhat less than the diameter of the stud 42. The section 43 is simply slipped onto the stud 42 where it is retained by its natural elasticity.

Various resilient materials having good insulating properties may be employed. A high grade pure gum rubber is very satisfactory. Synthetic materials such as neoprene may also be used, and are Preferable to natural rubber in certain cases because of their greater resistance to attack by agents which cause the deterioration of natural rubber.

The contact springs of the relay may be ad- Justed before the bracket as and associated parts are assembled on the heel piece. then placed on the heel piece and the screw 4| is inserted, the position of the bracket being such that the resilient member 433 is well clear of the contact springs. The screw ii should be turned in far enough to hold the bracket flat on the heel piece but not enough to prevent rotation thereof. The bracket is then rotated on screw M to the position in which it appears in Fig. 1, and the screw ti is tightened up so as to hold the bracket securely in this position.

As can be seen from Figs. 1 and 3,.when the bracket 48 is properly assembled to the heel piece i2, as described in the foregoing, the resilient member 53 is brought into engagement with the edges of the make contact spring 26 and the break contact spring 2?, the springs becoming indented in the resilient material. The material yields to accommodate the springs and the overlapping material forms a resilient support both above and below each spring. If it should become necessary to readjust the relay at any time, the screw 4!, is loosened up and the bracket 50 is rotated far enough in a clockwise direction so that the resilient member 13 is out of the way. After the adjustment is completed the bracket 60 is moved back to operative position and the screw M is tightened up again.

The adjustment of the bracket kill and resilient member 43 is not critical. Care should be taken, however, to insure that the member 13 is actually in good contact with the springs so that the latter indent the rubber, or other material of which the member :13 is composed, to a substantial degree, as indicated in Fig. 3.

The winding H of the relay is provided with suitable terminals such as Ed by means of which it may be connected in an electrical circuit. The contact springs also have integrally formed terminals such as 5! for connecting them in the circuits which they are intended to control.

When the relay is energized the armature It is attracted by the core it and the arm l5 moves the working contact spring 28 upward. Spring 28 immediately engages the bushing 29, whereupon the working contact spring 25 is moved upward also. Thus the contact on spring 28 is brought into engagement with the contact on make contact spring 21, while the contact on spring 25 is separated from the contact on the breakcontact spring 26.

Considering the operation of the springs 28 and 21 somewhat more in detail, the distance traveled b the contact on spring 28 before it engages the contact on spring 21 is variable, but may be about .010 inch, for example. This is the length of the-contact gap when the relay is deenergized. The distance traveled by the contact on spring 2! after it is engaged by the contact on spring 28 is also variable, but should not be so great that the spring 2! becomes permanently displaced relative to the resilient member 43.

The bracket is The travel may be, for example, as much as .018 inch without any danger of permanent displacement. When the contact on spring 21 moves upward, due to its engagement by the contact on spring 28, a warping action of spring 21 takes place, which reduces the distance the spring has to move upward at the point where its edge is engaged by the resilient member 43. This distance is small enough so that it is readily accommodated by the elasticity of the member 43 and no perceptible slipping of the spring 21 relative to member 43 occurs. When the relay is deenergized, therefore, both springs resume the normal position to which they have been adjusted.

As indicated hereinbefore, the armature I4 is sharply attracted upon the energization of the relay which brings the contact on spring 28 suddenly into engagement with the contact on spring 21, striking it a blow which in an ordinary relay would be apt to produce contact bounce. This effect is entirely eliminated in my improved relay, however, by the resilient member 43 which engages the contact spring 21 and resiliently supports the same as described, entirely preventing vibration of the contact spring.

When the relay is deenergized, the contact springs resume the position in which they are shown, spring 28 separating from spring 2! and spring 25 coming into engagement with spring 26. The closing of this back contact takes place suddenly, but there is no danger of contact bounce, due to the resilient support for spring 26 which prevents vibration thereof.

The resilient member 43 is common to the contact spring 26 and 21 and could support one or two additional contact springs as well. In the case of a relay having an unusually large spring combination, the resilient member may be made somewhat longer so as to take care of all the make and break contact springs The arrangement described is completely efi'ective, as has been demonstrated by numerous tests. Relays with various spring combinations showing contact bounce upon test have been equipped with the invention and re-tested, with the result that no contact bounce could be detected. As regards the life that. may be expected, a relay provided with a resilient supporting member 43 made from a high grade of natural rubber has been energized and deenergized 65,000,000 times without any appreciable change in the resilient member or decrease in its effectiveness.

The invention having been described, that which is believed to be new and for which the protection of letters patent is desired will be pointed out in the appended claims.

I claim:

1. In a relay, 9. contact spring, a second contact spring adapted to engage said first contact spring to close an electrical circuit, and a resilient member pressing against the edge of said first contact spring to prevent a momentary opening of said circuit by vibration of said first spring when the same is engaged by said second spring.

2. In a relay, a working contact spring, a second contact spring adapted to be engaged by said working contact spring. and a fixed body oi resilient insulating material in which the edge of said second contact spring is indented, whereby vibration of said second contact spring responsive to its engagement by said working contact spring is prevented.

3. In a relay, a working contact spring, a second contact sp g ad pted to be engaged by said working contact spring, nd a body of resilient material pressing against the edge of said second contact spring near the point where it is engaged by said working contact spring, said body having sufiicient elasticity to permit said second contact spring to yield when the same is engaged by said working contact spring.

4, In a relay, 9. working contact spring having a contact at the end, a second contact spring having an offset portion bearing a contact adapted to be engaged by the contact on said first spring, and a body of resilient material pressing against the edge of said second spring approximately at 6. In a relay, a plurality of working contact springs, a plurality of interspersed contact springs cooperating with said working contact springs, respectively, said cooperating contact springs having corresponding edge portions which are in alignment with each other but are not in alignment with any edge portions of said working contact springs, and a body of resilient insulating material pressing against said aligned edge portions to prevent vibration of said cooperating contact springs when the same are engaged by said working contact springs.

7. In a relay, a plurality of working contact springs, a plurality of springs cooperating with said working contact springs, respectively, said cooperating prings having sections which are out of alignment with the corresponding sections of said working contact springs, a body of soft rubher, and means for supporting said body with one side thereof pressing against the said sections of said cooperating contact springs in a direction which is substantially at right angles to the direction of movement of said working contact springs.

8. In a relay, a working contact spring, a second spring cooperating with said first spring, a heel piece, means for supporting said springs on said heel piece, a body of resilient insulating material, and means for adjustably supporting said body on said heel piece in two positions in one of which the body presses against the edge of said second spring to prevent contact bounce when the second spring is engaged by the first spring and in the other of which the spring is disengaged by said body and is free for adjustment.

9. In a relay, a working contact spring. a second spring cooperating with said first spring, a heel piece, means for supporting said springs on said heel piece, a body of resilient insulating material mounted on said heel piece so as to bear against the edge of said second spring to prevent contact bounce when the second spring is engaged by the first spring, and means supporting said body on said heel piece adapted to permit the said body to be moved out of engagement with said spring to facilitate adjustment thereof.

ARTHUR J. JOHNSTON.

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