US3889131A

US3889131A - Long life reliable relay

Info

Publication number: US3889131A
Application number: US410719A
Authority: US
Inventors: Jack B Speller
Original assignee: Individual
Current assignee: Individual
Priority date: 1973-10-29
Filing date: 1973-10-29
Publication date: 1975-06-10
Anticipated expiration: 1992-06-10

Abstract

A long life reliable relay for applying a voltage to a load in which the voltage is coupled to the load through a first contact assembly preferably comprising a plurality of radially resilient wheels on a common axle and adapted to be moved along a second contact assembly made up of a plurality of spaced contacts adjacent ones of which are connected by resistance elements such as zener diodes stepwise to reduce the resistance between the voltage and the load from an initially high value to a substantially direct connection as the contacts of the second assembly are successively engaged with the potential increment applied to the load from step to step being below that which would result in arcing.

Description

United States Patent 11 1 Speller 1 June 10, 1975 1 1 LONG LIFE RELIABLE RELAY 21 Appl. No.1 410,719

521 US. Cl. 307/136; 317/11 c 51 1m. (:1. 110111 9/30 [58] Field of Search 307/134-139;

317/11 C, 11 R, 11 A, 11 B, 11 D, 11 E; 200/144 AP, 11 DA, 10, 16 R, 154; 338/187; 335/126,128, 177

OTHER PUBLICATIONS Silicon Zener Diode and Rectifier Handbook, TK

7872, S4 M66, 1961 rev. pages 90-91.

Primary ExaminerRobert K. Schaefer Assistant Examiner-M. Ginsburg Attorney, Agent, or Firm-Shenier & OConnor ABSTRACT A long life reliable relay for applying a voltage to a load in which the voltage is coupled to the load through a first contact assembly preferably comprising a plurality of radially resilient wheels on a common axle and adapted to be moved along a second contact assembly made up of a plurality of spaced contacts adjacent ones of which are connected by resistance elements such as zener diodes stepwise to reduce the resistance between the voltage and the load from an initially high value, to a substantially direct connection as the contacts of the second assembly are successively engaged with the potential increment applied to the load from step to step being below that which would result in arcing.

14 Claims, 6 Drawing Figures SHEET PATENTEUJUH 10 I975 w mi LONG LIFE RELIABLE RELAY BACKGROUND OF THE INVENTION There are known in the prior art various forms of relays which serve to make or break one or more connections in an electrical circuit in response to a variation in a condition in that or another electrical circuit. After a period of time in use, relays of the prior art develop defects which interfere with proper functioning of the relay. Either the device does not close properly to make a good circuit or .it will not open as a result of welding of the contacts. Tests have shown that the best relays of the prior art have a failure rate of about 30 failures per 100,000 operations.

In addition to the defects of failure properly to close or failure to open, the contact resistance of relays of the prior art tends to increase as the unit ages. In order to provide a desired high current through a relay of the prior art, the magnetic pull of the operating solenoid must be relatively great.

The principal cause of the defects of relays of the prior art pointed out hereinabove is arcing between the contacts when the relay makes and when the relay breaks. This arcing causes relatively rapid erosion of the contacts. It also results in bridging as a result of contact material buildup on the contacts, interfering with proper operation thereof. Arcing further may result in contacts welding closed.

I have invented an improved long life relay which overcomes the defects of relays of the prior art. Possibility of arcing in my relay is substantially reduced as contrasted with relays of the prior art. My relay reduces both erosion of the contacts and undesirable buildup of contact material on the contacts. My relay is more certain in operation then are relays of the prior art. It has an appreciably lower failure rate than do relays of the prior art. It has a longer life in use than do relays of the prior art.

SUMMARY OF THE INVENTION One object of my invention is to provide an improved relay which overcomes the defects of relays of the prior art.

Another object of my invention is to provide an improved relay in which the possibility of arcing between the contacts is minimized.

A further object of my invention is to provide an improved relay in which erosion of the contacts is minimized.

A still further object of my invention is to provide an improved relay in which buildup of contact material is minimized.

Still another object of my invention is to provide an improved relay having a failure rate which is appreciably lower than that of relays of the prior art.

A still further object of my invention is to provide an improved relay of relatively small size.

Yet another object of my invention is to provide an improved relay which requires relatively low power for its operation.

Other and further objects of my invention will appear from the following description.

In general, the preferred embodiment of my invention contemplates the provision of an improved relay in which resistive elements such as diodes are connected between adjacent pairs of a stationary row of contacts spaced along the line of movement of a movable volt age carrying contact assembly which preferably comprises a plurality of radially resilient wheels carried by a common axle for stepwise reduction of the resistance between the movable assembly and the load connected to the last contact of the series so that the potential increment applied to the load as each contact of the series is engaged does not exceed the arcing potential.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings which form part of the instant specification and which are to be read in conjunction therewith and in which like reference numerals are used to indicate like parts in the various views:

FIG. 1 is a partially schematic plan view of one form of my long life reliable relay.

FIG. 2 is a partially schematic sectional view of the form of my relayshown in FIG. 1 taken along the line 22 of FIG. 1.

FIG. 3 is a partially schematic plan view of an alternate form of my long life reliable relay.

FIG. 4 is a plan view of yet another form of my long life reliable relay.

FIG. 5 is a plan view ofa still further form life reliable relay with a part broken away.

FIG. 6 is a fragmentary sectional view of the form of my relay shown in FIG. 5 taken along the line 6-6 thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIGS. 1 and 2 of the drawings, one form of my improved relay indicated generally by the reference character 10, includes a movable contact assembly, indicated generally by the reference character 12. The structure of the assembly 12 is shown and described in my copending application Ser. No. 128,819 filed Mar. 29, 1971, for Low Noise Long Wearing Electrical Contact, now abandoned. As is pointed out in the copending application, the assembly 12 includes a plurality of wheels 14 provided with circumferentially extending radially staggered slots 16 which render the wheel radially resilient. Preferably, the outer periphery of each wheel 14 carries a coating 18 of contact material such, for example, as gold or the like. The wheels 14 are carried by a common axle 20 which may, for example, be supported in slots 24 formed in the sides of a carrier 22. Carrier 22 is provided with a boss 26 to which the voltage at a terminal 30 to be coupled to a load may be connected by a conductor 28. Further, the boss 26 may receive a rod 32 connected to the armature 34 of a solenoid 36 adapted to be energized to move the assembly 12 in a manner to be described.

As is pointed out more fully in the copending application, the axle 20 may be secured in the slots 24 and the wheels 14 permitted to rotate on the axis. Alternatively, the wheels may be secured to the axle 20 and the axle 20 permitted to rotate relative to the carrier 22. Preferably, means is provided for urging the wheels 14 into intimate contact with each other. It will readily be appreciated that the carrier 22, axle 20 and the wheels 14, all are formed of conductive material so that the voltage at terminal 30 is coupled to the peripheries of the wheels.

The assembly 12 is adapted to be moved in the direction of the arrow in FIGS. 1 and 2 along the surface of a support 38 of any suitable insulating material such as glass so as successively to engage spaced contacts 40,

of my long 42, 44, 46 and 48 carried by the support 38. I prefer to use the contact assembly 12 in my relay since it ensures contact with the contacts such as contact 40 on support 38 with a minimum of pressure exerted on the carriage 22. It will readily be appreciated that with the assembly 12 positioned over the contact 40, for example, if one of the wheels is dirty" at the contact spot, the other wheels will make effective contact. Moreover, since the wheels rotate, the probability is that a clean spot will engage the contact on the next operation. An additional advantage of the assembly 12 is that contact bounce is substantially eliminated owing to the radial resilience of the wheel. The assembly is able to withstand high shock and vibration. Since the wheels rotate they require very little force to move them over the surface of the support 38.

In my improved relay, I connect pairs of back-

toback zener diodes

50 and 52

betweens contacts

42 and 44, 44 and 46 and 46 and 48. Contact 48 is provided with a shank 54 for connection to the load 56. It will be seen that the first contact 40 has no connection to the load, so that it is an inactive or electrically dead contact. All of the contacts extend above the surface of the support 38. When the assembly 12 moves relative to the contacts, wheels 14 first engage the edge of the contact 40 which serves to line up the wheels in the holder and to ensure good contact between the wheels and the axle and between the axle and the holder 22. It will be appreciated that the spacing between adjacent contacts is such that the wheels 14 engage the next contact before they leave the preceding contact.

In my improved relay, I prevent arcing as contact is made by ensuring that the increment of potential applied to the load as the assembly 12 moves from one contact to the next is less than the arcing value. By way of example, for gold in air, the voltage transferred from contact to contact as contact is made should be less than about 14 volts to ensure against arcing. By way of example, let us assume that each of the

zener diodes

50 and 52 has a breakdown voltage of volts, that a voltage of 28 volts is applied to terminal 30 and that the solenoid 36 is energized to move the carrier 22 to the right as viewed in FIGS. 1 and 2. As a result, the wheels 14 first engage the edge of the contact 40.

As has been pointed out hereinabove, engagement of the wheels with the contact 40 serves merely to align the wheels 14 in the carrier 22 and ensure good electrical contact between the parts of the movable contact assembly 12. As the carrier 22 continues to move it engages contact 42. Under these conditions, very little current will flow since three diodes of each polarity between contact 42 and the load 56 have an overall breakdown voltage of 30 volts, whereas only 28 volts has been applied to the terminal 30. Upon continued movement of the carrier 22, wheels 14 engage contact 44 before leaving contact 42. When that occurs, only two of the zener diodesof each polarity are effective between the terminal 30 and the load 56. Consequently, only about 8 volts is applied to the load 56 as wheels 14 engage contact 44. This potential clearly is not high enough to result in an arc. Further movement of the carrier 22 brings the wheels 14 into engagement with contact 46 to cut out one of the diodes which has been interposed between terminal 30 and load 56. The result is that an additional 10 volts is applied to the load and the total load voltage is 18. Finally, as the wheels engage contact 48, the full voltage from terminal 30 is applied to the load. The voltage jump, however, as the last contact 48 is engaged is only 10 volts, so that no arcing occurs. It will readily be appreciated that the reverse occurs when contact is broken and carrier 22 moves to the left as viewed in FIGS. 1 and 2.

While I have shown back to

back diodes

50 and 52 between each pair of adjacent active contacts, it will readily be appreciated that only a single diode need be employed between each pair of adjacent contacts where a DC. voltage is employed at terminal 30. Owing to the fact that zener diodes are available up to 50 amperes peak, relatively small contacts can be employed to handle large currents. It will be understood that this is a peak application, since the contacts move relatively rapidly with relation to each other. Higher voltages can be accommodated by using a greater number of contacts and diodes. For example, 120 volts DC. at terminal 30 might require 12 zener diodes and 12 contacts. 120 volts A.C. might necessitate the use of 17 contacts and 17 back to back diode pairs owing to the peak value of the voltage.

Referring now to FIG. 3, I have shown an alternate form of my relay indicated generally by the reference character 58, including a movable contact assembly indicated generally by the reference character 60 similar to the assembly 12, but including only two wheels 14 by way of example. Any suitable means may be employed to move the assembly 60 from left to right as viewed in FIG. 3 over the surface of a support 62 carrying a plurality of spaced

contacts

64, 66, 68, 70, 72, 74 and 76. As in the form of my relay described hereinabove, the first contact 64 of the series is electrically inactive, serving only to align the wheels of assembly 60 and to assure good electrical contact between the parts thereof. Further, as in the form of my invention described hereinabove, the load 56 is connected to the last contact 76 of the series.

In the form of my relay shown in FIG. 3, rather than using diodes I employ a printed resistor 78 so connected to the contacts that the resistance gradually decreases as assembly 60 engages successive contacts in moving from left to right. It will further be appreciated that the contacts, as well as the resistance 78, may be printed. In general, where resistors instead of diodes are employed, the number of contacts usually is greater in order to ensure that the current and voltage values are under the critical values. In this instance, as in the case where diodes are used, the resistance is so selected that the voltage change in going from one contact to the next is less than the critical arcing potential of, say, 14 volts, or that the current is less than the critical value of 0.2 ampere if the potential change is greater. The approach represented by FIG. 3 is especially adaptable to high voltage applications where a very high number of diodes might be required in the form of the invention illustrated in FIGS. 1 and 2. As in the first form of my invention, the type of load may be resistive or inductive.

Referring now to FIG. 4, yet another form of my relay, indicated generally by the reference character 80, incorporates a movable contact assembly, indicated generally by the reference character 82, including a plurality of

contact fingers

84, 86, 88, and 92, adjacent ones of which are connected by resistors 94. The movable contact assembly 82 is adapted to be moved by any suitable means known to the art successively to bring the fingers into engagement with a stationary contact 98 carried by a support 96. As before, we eonnect the load 56 to contact 98. As the fingers successively engage contact 98 the resistance between terminal 30 and load 56 is reduced in steps to e sure that no arcing results. i'

Referring now to FIG. 5, I have shown a still further form of my relay indicated generally by the reference character 100 including a support 102 carrying a plurality of spaced

contacts

104, 106, 108 and 110 disposed along the locus of a circle. I connect back-

toback diodes

112 and 114 between

contacts

106 and 108 and between

contacts

108 and 110. Contact 104 is an electrically inactive contact. I connect load 56 to the contact 110.

The movable contact assembly indicated generally by the reference character 116 of the relay 100 is similar to the assembly 12 of the form of my invention illustrated in FIGS. 1 and 2. A rod 118 connects the assembly 116 to an armature 120 mounted for rotary movement on a pin 122 carried by base 102. I dispose a her metically sealed cover 126 on the base 102 so that all of the contacts of the relay are enclosed. A conductor 124 which permits of limited rotary movement of as sembly 116 extends through a sealed opening in cover 126 to terminal 30. It will be appreciated that the connection between load 56 and contact 110 likewise is made through a sealed opening.

I mount a yoke 128 of magnetic

material having legs

130 and 132 on the outside of the cover 126.

Legs

130 and 132 carry

respective windings

134 and 136 adapted to be energized from a potential source 138 through a switch 140. When the windings are energized the resultant magnetic field moves armature 120 in a counter-clockwise direction as viewed in FIG. 5 to carry the assembly 116 over the

contacts

104, 106, 108 and 110 to apply the voltage of terminal 30 to the load 56 in steps in the manner described in connection with the form of my invention illustrated in FIGS. 1 and 2. Any suitable means such as a spring 142 on pivot pin 122 returns armature 120 to its initial position against a stop 144 when

windings

134 and 136 are deenergized. Owing to the fact that the particular contact assembly 116 requires relatively little force to cause it to make effective electrical contact with the contacts of the set, I am able to use the hermetically sealed container and rely on the magnetic coupling to the armature 120 to drive the assembly.

The operation of all forms of my relay will be apparent from the description given hereabove. In each instance, as the movable contact assembly moves relative to the stationary contacts or contacts, the voltage is applied to the load in steps. The steps, moreover, are below the critical arcing potential. I'ensure that the current is below that which would result in arcing.

It will be seen that I have accomplished the objects of my invention. I have provided a relay which overcomes the defects of relays of the prior art. My relay minimizes arcing as contact is made and broken. It reduces erosion and buildup of contact material. It has an appreciably lower rate of failure than do relays of the prior art. It is compact and relatively inexpensive to construct.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of my claims. It is further obvious that various changes may be made in details within the scope of my claims without departingfrom the spirit of my invention. It is, therefore, to be understood that my invention is not'to be limited to the specific details shown and described.

Having thus described my invention, what l claim is:

1. A relay for applying a voltage to a load including a combination, a first contact, a plurality of spaced second contacts, means mounting said first contact and said second contacts for relative movement to cause said first contact successively to engage said second contacts, respective zener diodes connected between adjacent said second contacts, and means for applying said voltage and said load between said first contact and the last second contact engaged by the first contact, the breakdown voltages of said diodes being such as to ensure that the voltage change at the load is less than the breakdown potential between the first contact and the second contact engaged thereby as the first contact successively engages the second contacts.

2. A relay as in claim 1 in which said first contact comprises a plurality of inherently radially resilient wheels of the same size and means mounting said wheels for rotary movement on a common axis.

3. A relay as in claim 2 including a hermetically sealed housing containing said wheels and said second contacts and means outside said housing for moving said wheels relative to said second contacts.

4. A relay as in claim 3 in which said moving means comprises means providing a magnetic coupling through said housing.

5. A relay as in claim 1 including a hermetically sealed housing enclosing said first and second contacts and means outside said housing for moving said contacts relative to each other.

6. A relay as in claim 5 in which said second contacts are disposed along the locus of a circle and in which said mounting means comprises an arm mounting said first contact for movement along said locus.

7. A relay as in claim 6 in which said means for moving said contacts is a magnet.

8. A relay as in claim 1 wherein said zener diodes are connected back-to-back between adjacent second contact.

9. A relay for applying a voltage to a load including in combination, a contact assembly comprising a plurality of inherently resilient contact wheels of substantially the same size and means mounting said wheels for rotary movement around a common axis, a plurality of spaced generally flat contacts, means mounting said contact assembly and said flat contacts for movement relative to each other to cause the wheels of said contact assembly successively to engage said flat contacts to reduce frictional resistance between the wheels and the flat contacts, respective resistive elements connected between adjacent ones of said flat contacts, means for applying said voltage and said load across the contact assembly and the last of said flat contacts engaged by the contact assembly, the magnitude of said resistive elements being such as to ensure that the voltage change at the load is less than the breakdown potential between the contact assembly and the flat contact engaged thereby as the contact assembly successively engages said flat contacts.

10. A relay as in claim 9 in which said contact assembly engages a succeeding second contact before disengaging a preceding contact.

11. A relay as in claim 9 in which said flat contacts ments comprise back-to-back zener diodes connected are stationary and in which said contact assembly is between the adjacent flat contacts movable. t

12. A relay as in claim 9 in which said resistive ele- A relay m clam 9 m which resistive elements are zener diodes s ments comprise a printed resistor.

13. A relay as in claim 9 in which said resistive cle-

Claims

11. A relay as in claim 9 in which said flat contacts are stationary and in which said contact assembly is movable.

12. A relay as in claim 9 in which said resistive elements are zener diodes.

13. A relay as in claim 9 in which said resistive elements comprise back-to-back zener diodes connected between the adjacent flat contacts.

14. A relay as in claim 9 in which said resistive elements comprise a printed resistor.