US3636414A

US3636414A - Relay apparatus

Info

Publication number: US3636414A
Application number: US6529A
Authority: US
Inventors: Harold A Mcintosh; Hollis L Randolph; William W Chambers; Marvin M Graham
Original assignee: Robertshaw Controls Co
Current assignee: Robertshaw Controls Co
Priority date: 1970-01-28
Filing date: 1970-01-28
Publication date: 1972-01-18
Anticipated expiration: 1989-01-18

Abstract

A relay apparatus to operate in response to an induction from an electric current in a conductor and including a housing having a first contact mounted thereon. A flexible blade is carried by one end from the housing and carries a movable contact on its free end. Sensing means is responsive to a predetermined electrical current in the lead to provide a signal which is amplified to operate an actuator which flexes the blade to engage the movable contact with the first contact. The blade may be of nonlinear configuration and the actuator may move transversely thereto and engage such blade intermediate its ends to cause flexing thereof to engage the movable contact with the stationary contact and to continue flexing of such blade to move the movable contact across the surface of the first contact whereby the blade will remain flexed during contact closure and will tend to unflex when the actuator is retracted to apply a shearing force to any weld that may have developed between the contacts to thereby break such weld.

Description

United States Patent McIntosh et al.

[ Jan. 18, 1972 4] RELAY APPARATUS Primary ExaminerL. T. Hix [72] inventors: Harold A. McIntosh, South Pasadena; Hol- Ammey Fulwlder Patton Lee & Utecm its L. Randolph, Lakewood; William W. Chambers, Anaheim; Marvin M. Graham,

Seal Beach, all of Calif.

Assignee: Robertahaw Controls Company,

Richmond, Va.

Filed: Jan. 28, 1970 Appl. No.: 6,529

U.S. Cl ..317/l48.5 B, 335/204, 307/131, 317/D1G. 9 Int. Cl ..H0lh 9/00, l-lOlh 47/32 Field of Search ..317/l37, D16. 9, 148.5, 148.5 B; 336/105; 307/131; 335/204 References Cited UNITED STATES PATENTS 3,419,756 12/1968 Philbert et a1. ..317/16 [57] ABSTRACT The blade may be of nonlinear configuration and the actuator may move transversely thereto and engage such blade intermediate its ends to cause flexing thereof to engage the movable contact with the stationary contact and to continue flexing of such blade to move the movable contact across the surface of the first contact whereby the blade will remain flexed during contact closure and will tend to unflex when the actuator is retracted to apply a shearing force to any weld that may have developed between the contacts to thereby break such weld.

16 Claims, 26 Drawing Figures PATENTEI] JAN18EJ72 3.636.414 sum 2 -.or .33

.53 l VENT :36 Z Hm, mafia 57 HOLLIS 1.. RANDOL PH (4/ 24/ 7 BY WILL/AM Ml, Cl/IMBEEJ F v MAI VIN M.

RELAY APPARATUS BACKGROUND OF THE INVENTION I Field of the Invention The present invention relates to a relay which is responsive to a predetermined current in an electrical lead to actuate an operator circuit and which may employ a switch having con-' tacts which are slid on one another when the switch is opened to thereby shear any weld which has been developed therebetween.

2. Description of the Prior Art Current-sensing relays known to applicants frequently provide insufficient power to operate the relay in a circuit having a relatively large load thereon. Further relays have been proposed which include means for moving one contact across the surface of the other when the relay is deenergized to thereby break any weld formed between the contacts, but these relays generally employ cams, or linkages to effect the sliding between thecontacts thereby resulting in a requirement of relatively large forces for operation. Also, many relays of this type are of such configuration that current conduction through the switch is relatively poor. Relays have been proposed which include flexible blades afiixed on one end to the relay body and carrying a movable contact intermediate its ends and projecting therebeyond to form an overhang which is engaged by a transversely moving actuator to close the contacts and slide one relative to the other. However, such an arrangement does not provide sufficient contact sliding for many applications.

SUMMARYOF THE INVENTION The relay of'present invention is characterizedby a movable contact carried from a blade for selective engagement with a stationary contact. A sensing means is responsive to a predetermined current in an electrical lead to actuate an amplification means which operates an actuator coupled to such blade to thereby close the switch.

The blade, is preferably flexible and of nonlinear configuration and is affixed on one end to the housing and has the movable contact carried from its free end. The actuator engages the blade intermediate its ends and has sufircient travel transverse to the blade after the contacts are engaged to flex and partially straighten the blade to cause sliding of the movable contact on the stationary contact whereby when the actuator is deenergized to enable the relay to open the blade will tend to slide the movable contact across the stationary contact to breakany weld that may have developed between the contact An object of the present invention is to provide a relay of the type described which has a relatively high current rating and requires a relatively low amount of power for operation.

Another object of the present invention is to provide a relay of the type described wherein the blade carrying the movable contact serves as a current carrying member and, while providing relatively low spring tension, provides sumcient cross-sectional area to avoid electrical heating-during conduction of current therethrough.

It is a further object of the present invention to provide a relay of the type described wherein the opening forces are utilized to cause sliding of the contacts on one another rather than providing for a rocking movement between such contacts, it being noted that any weld accidentally formed between the contacts would be weakest in shear.

A further object of the present invention is to provide a relay of the type described wherein the fixed end of the blade is mounted from the contact housing at a point offset from the plane of the stationary contact to thereby enhance the tendency of the movable contact to slide on the stationary contact when the actuator is deenergized and the blade unflexes.

It is still another object of the present invention to provide a contact of the type described wherein the con cts will not bounce apart upon initial engagement thereof to thereby avoid arcing and consequent welding therebetween.

It is a still further object of the present invention to provide a relay of the type described wherein the contacts are slid across one another during making and breaking thereof to wipe the surface oxides and impurities to maintain good contact and, consequently, good electrical conduction therebetween when the contacts are closed. Such wiping action also tends to maintain the contact surfaces smooth thereby avoiding any tendency of the contacts to lock together due to interlocking irregular contacting surfaces. Further, the sliding of the contacts wipes any dielectric film from between the contacts.

These and other objects and the advantages of the present invention will become apparent from the consideration of the following detailed description when taken in conjunction with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS FIG. 7 is a horizontal sectional view taken along the line 7 7 of FIG. 4; 1

FIG. 8 is a vertical sectional view taken along the line 88 of FIG. 3;

FIG. 9 is a vertical sectional view taken along the line 99 of FIG. 2;

. FIG. 10 is a vertical sectional view taken along the line I0 10 of FIG. 2; I

FIG. 11 is a horizontal sectional view taken along the line ll-ll ofFIG. 4;

FIG. 12 is a horizontal sectional view taken along the line l2l2ofFlG. ll;

FIGS. 13 through 16 are diagrammatic views, in enlarged scale, of a flexible blade carrying the movable contact included in the relay shown in FIG. 1, such blade being shown in several different positions;

FIG. 17 is an electrical schematic of a circuit which may be utilized with the relay shown in FIG. I;

FIG. 18 is a vertical sectional view of a second embodiment of the current-sensing relay of present invention;

"FIG. 19 is a vertical sectional view taken along the line 19- 19 of FIG. 18;

FIG. 20 is a horizontal sectional view taken along the line 20-20 of FIG. 18;

FIGS. 21 through 24 are diagrammatic views showing the contact-carrying blade in several different positions; and

FIGS. 25 and 26 are diagrammatic views of modifications of the current-sensing relay shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 3, the current-sensing relay of present invention includes, generally, a housing 31 which has one end of a flexible electrically conductive arcuate blade 35 (FIGS. 13-17) mounted thereon and carrying a movable contact 37 on its free end for engagement with a stationary contact 39 disposed thereunder. The arcuate blade 35 is engaged intermediate its ends by the lower end of a spacing post, generally designated 43, interposed between such blade and the free end of a cantileverally mounted, ferromagnetic arm 47 (FIGS. 3 and 17). An actuator coil 51 is disposed under the inter mediate portion of the ferromagnetic arm 47 and has current thereto controlled by the power circuit of a silicon-controlled rectifier (SCR) 53. The gate of the SCR 5 3 is connected with dary coil 57 will impose a triggering current on the gate of the SCR 53 to initiate current through the actuator coil 51 to attract the arm 47 and push the blade 35 downwardly to the position shown in FIG. 13. After the

contacts

37 and 39 engage, the actuator coil continues to attract the arm 47 downwardly to flatten the flexible blade 35 to the position shown in FIG. 14 thereby sliding the movable contact 37 to the left on the primary contact 39 to provide a wiping action between the contacts and maintain the flexible blade in such flattened position until the relay is deenergized. When current in the leads 65 drops below the actuation level, the SCR 53 will be rendered nonconductive thereby discontinuing current in the coil 51 and enabling the flexible blade 35 to unflex and force the movable contact 37 to the right on the stationary contact 39 as shown in FIG. thereby effecting a shearing action between such contacts to shear any weld that may have been formed therebetween.

Referring to FIGS. 1 through 5 the housing 31 includes a plastic base 75 which is formed with a bottom wall 76 and a pair of opposed

upstanding sidewalls

77 and 79. A cover, generally designated 81, is received on the base and includes a top wall 83 formed with a pair of downwardly extending

opposed end walls

85 and 87 which cover the open ends of the base and are formed on their marginal edges with inwardly bent peripheral lips 91 which overlie the marginal ends of the

respective sidewalls

77 and 79. Referring to FIG. 1, the end wall 87 is fonned with oppositely projecting mounting tabs 80 and 82 for mounting the relay to a wall. As best seen in FIGS. 1 and 4, the cover 81 is also formed with downwardly bent ears, generally designated 93 and 95, that are in juxtaposition with the

base sidewalls

77 and 79 and out of which are pressed upwardly projecting and inwardly bent resilient holding tabs 97 and 99, respectively, which engage in depressions .101 and 103 formed in the

respective sidewalls

77 and 79 and abut against the upper ends thereof to hold the cover 81 securely on the base.

Referring to FIGS. 3 and 13, the fixed end of the flexible blade 35 is turned back under itself and forms a mounting tab 105 which has a mounting tab 106 of a terminal, generally designated 107, extending thereover and secured in position by a rivet 109. The terminal 107 has its one extremity bent downwardly and extends through a passage 110 in the bottom wall 75 of the base and extends therebelow to form a plug prong I13.

Referring to FIG. 12, the passage 110 is formed on one side with a reduced-in-cross-section keyway 111 and the downwardly bent plug prong 113 is formed with a reduced-incross-section key 115 which interfits the keyway I11 whereby the downwardly turned terminal prong 113 may be inserted downwardly through the passage 110 and the entire terminal 107 then shifted sideways to fit the key 115 in the keyway 111. Then when the rivet 109 is inserted the terminal 107 will be held firmly in position with the key 115 held captive in the keyway 11.

Referring to FIG. 2, the stationary contact 37 is carried from a terminal, generally designated 121, similar to the terminal 107 and formed with a downwardly projecting plug prong 123 which is formed with a key similar to that shown in FIGS. 11 and 12 for interlocking with a cooperating keyway in the bottom wall 75 of the housing base. Still referring to FIG. 2, a stationary contact 125 is disposed above and in alignment with the movable contact 37 and is carried from a terminal, generally designated 127, which is formed with a downwardly projecting plug prong 129 having a key similar to that shown in FIG. 11 formed therein for interfitting a cooperating keyway in the base bottom wall 73.

Referring to FIGS. 2 and 17, the rear end of the actuating arm 47 rides on the top of a vertical support post defined by one leg 131 of a horseshoe-shaped magnet, the other leg of which defines a core 153 for the relay coil 51. The post 131 is formed with a pair of transversely aligned outwardly opening notches 135 (FIG. 4) and with a rearwardly opening central notch 137. A resilient retaining clip, generally designated 141, (FIG. 2) extends upwardly along the backside of the post 131 and is formed with a pair of transversely spaced upwardly projecting ears 143 which are received in the side opening notches 135. The clip 141 is formed with a retaining tab 147 that is offset rearwardly from the body of the clip and projects upwardly through the central notch 137 and is then bent forwardly over the rear extremity of the arm 47 and turns downwardly to engage such arm in front of the post 131 to maintain the forward extremity of such arm biased downwardly.

The actuator coil 51 is disposed centrally under the arm 47 and, as indicated above, has its central core formed by the magnet leg 153 (FIGS. 2 and 7), the upper extremity of which leg serves as a stop for the intermediate portion of the arm 47 to positively limit downward movement of the free extremity thereof. Still referring to FIG. 7, the central portion of the arm 47 is formed with upwardly and outwardly flared wing portions 155 to form a central downwardly projecting apex 157 that engages the stop defined by the upper extremity of the core 153.

Referring to FIG. 6, the underside of the rear extremity of the arm 47 is formed with a downwardly opening recess 159 that defines a pair of downwardly projecting legs I61 and 163 disposed on opposite sides thereof and which ride on the upper end of the support post 131 whereby the rear extremity of the arm 47 will be supported from such legs 161 and 163 and the forward extremity supported by the apex 157 (FIG. 7) when the arm 47 is pulled downwardly to thereby provide a stable three point support to prevent rocking and tilting thereof.

The spacing post 43 interposedbetween the actuating arm 47 and the intermediate portion of the blade 35 includes an upwardly projecting peg 143 (FIG. 3) received in an elongated slot 145 (FIG. 4) formed in the front extremity of such arm and a downwardly projecting peg 147 (FIG. 13) received loosely in a bore through the blade 35 to thereby provide for shifting of the free end of such blade relative to the arm 47 as such blade is flexed.

Referring to FIGS. 1 and 8, the retaining bale 61 is generally U-shaped and has its opposite legs projecting through slots formed in opposite sides of the top wall 83 of the cover 81, such legs projecting downwardly and being formed with through downwardly opening slots 17] and 173 that define forks which receive opposite extremities of a magnetically conductive mounting bar, generally designated 175, disposed within the cover 81.

Theend walls

85 and 87 are fon'ned with

respective slots

177 and 179 and the opposite extremities of the mounting bar extend through the slots 171 and 173 in the loop 64 and the forks defined by the extremities of the loop are pinched closed thereon. The ends of the mounting bar 175 project beyond the

slots

177 and 179 in the cover 81 and are staked over on their projecting extremities for positive retention.

Referring to FIGS. 2, 5 and 8, a bobbin, generally designated 183, is formed from a synthetic plastic and includes a hollow central passage (FIG. 8) for receipt of the mounting bar 175 and has

external flanges

187 and 189 which are spaced apart to define a spool 191 therebetween for receipt of the windings of the secondary coil 57 included in the sensing transformer 59.

Referring to FIG. 5, the

flanges

187 and 189 are each formed on their one side with respective projecting ears 193 and 195 which are formed with open-ended retaining notches that receive and frictionally hold

respective leads

197 and 199 of a resistor 201 utilized in the circuitry for the relay. The bobbin 183 includes a pair of laterally projecting

opposed jaws

205 and 207 for receipt therebetween of the SCR 53 and are formed on their respective projecting extremities with inwardly turned confronting

lips

211 and 213 for retention of such SCR. Projecting opposite the

jaws

205 and 207 are opposed inwardly tumed resilient flanges 217 and 217 (FIG. 3) which receive a resistor 219 therebetween, such resistor also being utilized in the control circuitry.

Referring to FIGS. 2 and 10, a coil terminal, generally designated 225, is disposed adjacent the actuator coil 51 and is connected with one end thereof. The terminal 225 projects downwardly through a passage 229 included in the bottom wall 76 of the base, such passage being formed on its upper extremity with oppositely angled flares 231 and 233. The terminal 225 is somewhat malleable and includes a pressed out perpendicularly projecting portion defining a limit tab 226 for engaging one side of the housing wall 76. Such terminal 225 is formed with a reduced-in-cross-section area 235 to form oppositely disposed notches for receipt of a staking tool whereby such terminal may be inserted in the passage 229, the tab 226 engaged with one side of the wall 76 and the terminal staked over to-form oppositely extending

rivet portions

237 and 239 which engage the flares 231 and 233, respectively, to retain such terminal in position.

Referring to FIGS. 4 and 17, a second coil terminal 240,

similar to the terminal 225, is connected with the anode of the SCR 53. One end of the resistor 201 (FIG. 5) is connected with a manual switch terminal, generally designated 24], which is formed with a reduced-in-cross-section area 243 for receipt in a through passage 245 in the bottom wall 76 of the housing base. The upper extremity of the passage 245 is formed with oppositely angled flares 246 and 247 and the upper extremity of the terminal 241 is split for spreading to form oppositely angled retaining legs 248 and 249 which cooperate with the shoulder 250 formed by the bottom end of the reduced-incross-section area 243 to retain such terminal in the housing base.

The electrical schematic shown in FIG. 17 depicts an electrical circuit which may be employed with the relay of present invention and includes a transformer 251 having its primary coil in circuit with a source plug 252 and its secondary coil connected in series with the power circuit of the SCR 53 and with the actuator coil 51. A capacitor 253 is connected across the secondary coil of the transformer 251 to control the voltage spikes.

A freewheeling resistor 257 is connected across the actuator coil 51 to provide a path for current flow during nonconductive portions of the SCR controlled or current cycle to thereby reduce hum.

Connected in parallel with the gate of the silicon-controlled rectifier 53 is the resistor 201 which leads to the terminal 241 for connection with one side of a manual switch 263 by means of a lead 262. The other side of the switch 263 is connected with the side of the secondary coil 57 opposite the cathode of the SCR 53 whereby such SCR may be triggered by closing of such manual switch 263.

When the relay is assembled, the base and cover 81 are formed separately and the

terminals

107, 123, 129, 225, 240 and 241 are installed as described above. The bobbin 183 serves as a jig for winding the coils of the secondary coil 57 of the sensing transformers 59 thereon and for holding the SCR 53 and

resistors

201 and 219 during soldering of the leads thereof. First the secondary coil 57 is formed by wrapping windings on the spool 191 and the SCR 53 may then be inserted between the

flexible jaws

205 and 207. The resistor 2.01 may then be positioned adjacent the secondary sensing coil 57 with its terminals received between the jaws defined by the projecting tabs 193 and 195 (FIG. 5). The resistor 219 is then inserted between the jaws 215 and 217 (FIG. 3) and the respective terminals are bent to the general configuration shown in FIG. 5 and the electrical leads between adjacent elements soldered. In this manner the bobbin 183 serves as a jig for holding the electrical components in position while their terminals are soldered to the respective leads.

The assembled relay is particularly useful for controlling a fan for blowing air over a plurality of independently actuated resistance heating elements and may be installed on a wall adjacent a furnace including such elements by inserting mounting screws through the mounting cars and 82 (FIG. I). A socket assembly, or assemblies, formed with receptacles for the respective plug prongs of the

terminals

107, 123, 225, 240 and 241 may then be mated with such terminals to connect the

terminals

123 and 107 with a blower for blowing air over a plurality of heating elements 267, the

terminals

225 and 240 with the source transformer 251 and the terminal 241 with the manual switch 263. The leads 65 to the independently actuated heaters are then threaded through the retaining bale 64.

When any one of the furnace heating elements 267 is energized the current in the electrical lead 65 thereto will induce a current in the secondary coil 57 of the sensing transformer 59 to impose a triggering signal on the gate of the SCR 53 thereby energizing the actuator coil 51 to pull the free end of the actuator arm 47 downwardly. Downward movement of the free end of the actuator arm 47 will pivot the flexible arm 35 about its right-hand end, as shown in FIG. 13, to cause the movable contact 37 to travel in a path somewhat oblique to the stationary contact 39 to thereby avoid direct striking thereof and consequent bouncing apart of the contacts which may result in arcing which may cause contact deterioration and possible welding together. Continued downward movement of the free end of the actuator arm 47 under the influence of the actuator coil 51 will cause the generally arcuately shaped flexible blade 35 to flatten somewhat to the position shown in FIG. 14 thereby moving the movable contact 37 leftward across the surface of the stationary contact 39 to provide a wiping action and cause the blade 35 to assume and maintain a stressed positron.

It is noted that travel of the free end of the arm 47 generally transverse to the blade 35 will be multiplied by the flattening of such blade to produce a greater amount of sliding of the movable contact 37 on the stationary contact 39 over that which would be provided by an equivalent amount of transverse travel of the central portion of a straight blade. Numerous blade configurations may be employed for providing similar results, some of which are shown in FIGS. 25 and 26.

It will be clear from FIG. 2 that the cantilever mounting of the arm 47 enables the intermediate portion of such arm to be spaced relatively close to the actuator coil core 153 to provide a relatively small airgap therebetween whereby energization of such core will strongly attract the intermediate portion of said arm thereby effecting a relatively large movement of the free end of the arm to effect relatively large downward movement of the intermediate portion of the flexible blade 35 to close the contacts and effect a relatively large amount of travel of the movable contact 37 across the surface of the stationary contact 39.

It is important that in its actuated position the actuator arm 47 is supported at its rear extremity from the top end of the vertical post 131 (FIGS. 4 and 6) by means of the downwardly projecting legs 161 and 163 and is supported intennediately on the top end of the actuator coil core 153 by means of downwardly projecting apex 157 to thereby assure an essentially three point support to provide a relatively stable condition for the actuator arm 47 thereby avoiding rocking thereof and consequently erratic operation.

It is also of importance that the apex 157 is somewhat elongated in the longitudinal direction of the arm 47 to provide a wearing surface that is relatively large while providing for contact with the core 153 along a line extending longitudinal to such arm. The chevron or somewhat V-shape presented by the upwardly and outwardly angled wings (FIG. 7) provides a configuration wherein the magnetic flux from the coil 51 will be heavily concentrated at the apex 157 thereby leaving only a relatively small portion of the total flux to assume a path through the airgap formed between the angled wings I55 and the top of the core 153. It is noted that the magnetic attraction of a body is inversely proportional to the square of the distance of such body from the magnetic source. Thus wearing of the apex 157 which causes the arm 47 to be positioned closer to the core 153 when the relay is actuated has only a minor effect on the composite airgap between the arm 47 and top of the core 153 thereby only slightly altering the magnetic attraction of the arm 47 to provide only a minor change in the operating characteristics of the relay. When the current in all the leads 65 from the respective furnace elements 267 is discontinued, the current on the gate of the SCR 53 will drop below the triggering level to thereby block current flow through the actuator coil 51 and release the arm 47 for upward pivoting of its free end under the influence of the flexible blade 35. The intermediate portion of the arcuate flexible blade 35 is then free to flex upwardly and draw the movable contact 37 across the surface of the stationary contact 39 as shown in FIG. 15. It is important that the entire initial movement of the movable contact 37 is linear travel across the surface of the stationary contact 39 to thereby utilize the entire unflexing force of such blade to shear any weld which may have been formed between such contacts. This is important because. such a weld would be weakest in shear.

Sliding movement of the movable contact 37 caused by unflexing of the spring blade 35 to its arcuate position is further enhanced by the fact that the free end of such blade tends to pivot upwardly and to the right about the fixed right-hand end of such blade (FIG. to thereby produce an additional component of travel to the right over that which would be provided by a blade having its fixed end disposed in the same plane as the free end.

If at any time it should be desirable to actuate the blower (not shown) when the heater elements 267 are not energized, the manual switch 263 may be closed to provide current flow through the resistor to produce a triggering current at the gate of the SCR 53 to energize the actuating coil 51 and repeat the above described contact closure.

The current-sensing relay shown in FIGS. 18 through 24 is similar to that shown in FIG. 1 except that the relay coil 275 is disposed above the actuating arm 47 and is carried from the housing by means of a mounting bracket 77. The core of the coil 275 is in the form of an inverted horseshoe 281 and the rear extremity of the actuating arm 47 is biased upwardly against one leg thereof by means of a retaining clip, generally designated 285, which is similar to the retaining clip 141 but partially inverted.

The free end of the actuating arm 47 carries a post, generally designated 289, which is connected with the intermediate portion of the electrically conductive r'esilient blade 35. Thus, when the coil 275 is energized, the free extremity of the arm 47 will be moved upwardly to pull the movable contact 37 upwardly into engagement with the stationary contact 125 and continued upward flexing of the central portion of the blade 35 will flex such blade to a more arcuate configuration and slide the movable contact 37 to the right across the surface of the stationary contact 125 as shown by the directional arrows in FIG. 22. When the relay coil 275 is deenergized, the arm 47 will be released and the flexible blade 35 will unflex to slide the movable contact 37 to the left across the stationary contact 125 as shown in FIG. 23 to thereby break any weld that may have developed between such contacts. Obviously, both the upper and lower

stationary contacts

125 and 39 may be utilized in a control circuit.

The blade configurations 35' and 35" shown in FIGS. 25 and 26 are representative of other blade configurations which would provide sliding of the respective

movable contacts

37 and 37" on respective stationary contacts 39' and 39" when a transverse actuating force is applied to such blade after initial contact engagement has been made.

From the foregoing detailed description it will be apparent that the current-sensing relay of present invention is straightforward in construction to provide a convenient and compact package which is relatively inexpensive to produce. The base and cover form a housing which is convenient to assemble and means is provided for conveniently securing the plug prongs in position in the base. Further, the bobbin for the secondary sensing coil provides a spool for such coil and forms a relatively convenient jig for mounting the electrical components during connection together thereof. Further, the elongated actuating arm is cantileverally mounted and the actuating coil core, which acts as a stop to limit downward travel of such arm, is disposed intermediate the ends of such arm to provide a relatively small airgap between such coil and arm to enhance the magnetic attraction therebetween and to enable such stop to act on a portion of the arm which travels through a relatively short arc to thereby reduce relay noise during activation thereof. In addition, the nonlinear configuration of the contact-carrying blade provides a transverse force which causes sliding of the movable contact on the stationary contact upon deactuation of the relay and the consequent wiping polishes the engaging contact surfaces each time the relay is actuated to thereby remove dielectric film and maintain the contact surfaces smooth to prevent mechanical hangup therebetween.

Various modifications and changes may be made with regard to the foregoing detailed description without departing from the spirit of the invention.

What is claimed is:

l. A current-sensing relay for operating in response to a predetermined electric current in a lead, said relay comprismg:

a housing including a ferromagnetic loop formed with a ferromagnetic bar;

a first contact mounted on said housing;

a movable contact disposed in engageable alignment with said first contact;

a blade carrying said movable contact;

electrical actuator means for moving said blade to selectively engageand disengage said contacts;

sensing coil means wound on said bar and mounted in circuit with said actuator means for sensing the current in said lead and responsive to said predetermined electrical current to produce an electrical signal;

amplifier means in circuit with said actuator means and sensing means and responsive to said signal to operate said actuator means and move said blade whereby said relay will operate in response to said predetermined electrical current.

2. A current-sensing relay as set forth in claim I wherein:

said blade is elongated, flexible and crooked and has one end affixed to said housing and carries said movable contact on its free end; and

said actuator means operatively engages said blade intermediate said one end and said movable contact to move said free end transversely and engage said movable contact with said first contact, and then continue transverse movement of the intermediate portion of said blade to further flex said blade and slide said movable contact across said first contact a sliding distance greater than it would be slid by an equivalent amount of transverse movement of the intermediate portion of a straight blade whereby when said actuator is released said blade will unflex and move said movable contact said sliding distance across said first contact to provide a relatively large contact breaking force.

3. A current-sensing relay as set forth in claim 1 wherein:

said amplifier means includes a silicon-controlled rectifier having its gate in circuit with said sensing means and its power circuit in circuit with said actuator means.

4. A current-sensing relay as set forth in claim 1 wherein:

said actuator means includes an arm having its front extremity projecting over said blade for engagement therewith, a mount carried on said housing for supporting the rear extremity of said arm and including a resilient holding clip projecting forwardly over the rear extremity of said arm and beyond said mount to bias said front extremity downwardly toward said blade.

5. A current-sensing relay as set forth in claim 1 wherein:

said housing includes a terminal receiving passage formed with a depression in one side for defining a keyway; and

said relay includes a plug terminal in circuit with one of said contacts and projecting through said passage to form a plug prong, said terminal being formed with a reduced-incross-section portion defining a key for complimentally interfitting said keyway whereby said terminal may be inserted in said passage, shifted laterally therein to fit said key in said keyway, and affixed to said housing to mount said terminal firmly on said housing.

6. A current-sensing relay as set forth in claim 1 wherein:

said housing is formed with a terminal receiving passage;

and

said relay includes a terminal for insertion in said passage and including a malleable rivet forming portion whereby said terminal may be inserted in said passage and said rivet forming portion riveted over to hold said terminal captive in said passage. 7

7. A current-sensing relay as set forth in claim 1 wherein:

said housing includes a base formed with a pair of oppositely disposed sidewalls formed on their exterior with respective clip-receiving recesses, said housing further ineluding a cover formed with a pair of oppositely disposed downwardly projecting sidewalls in juxtaposition with the walls of said base and formed with resilient clips for receipt in said recesses to lock said cover to said base.

8. A current-sensing relay as set forth in claim 1 wherein:

said housing includes a blade mount;

said actuator includes an an'n formed on its rear extremity with a pair of spaced apart legs carried on said mount, and is formed intermediately with a downwardly projecting apex; and

said housing includes a stop disposed adjacent said apex for engagement thereby to limit travel of said arm toward its contact closing position whereby said arm will be supported at three points when said relay is actuated.

9. A current-sensing relay as set forth in claim 1 that ineludes:

a bobbin fonned with a spool for winding said coil thereon and with a passage extending through the center of such spool for receipt of a magnetic conductor disposed in electrical inductive relationship with said lead.

10. A current-sensing relay as set forth in claim 2 wherein:

said blade is formed intermediately with a peg-receiving opening; and

said actuator means includes a peg which loosely interfits said opening whereby the intermediate portion of said eludes:

blade will be free to shift forwardly and rearwardly during actuation of said relay to facilitate alignment between said blade and actuator.

11. A current-sensing relay as set forth in claim 1 wherein:

said housing includes a mounting bar having its opposite ends connected with said loop and having said coil wound therearound.

12. A current-sensing relay as set forth in claim 11 wherein:

said housing is formed with a pair of slots for receiving the opposite extremities of said loop;

said loop is generallyU-shapcd and has its opposite extremities projecting through said slots and said opposite extremities are fonned with openings; and

the opposite extremities of said mounting bar project through said openings and are secured to said housing to affix said loop to said housing.

13. A current-sensing relay as set forth in claim 9 wherein:

said actuator means includes a plurality of electrical components; and

said bobbin includes a plurality of holding tabs forming cavities for receipt of said respective components.

14. An electrical switch as set forth in claim 1 wherein:

said actuator means includes an electromagnet having its core formed on one end with a stop, an arm coupled with said blade and overlying said core and formed with a V- shaped ferromagnetic portion disposed adjacent said stop and having its apex engageable therewith when said electromagnet is energized whereby said V-shaped portion will form a plate for a relatively lar e portion of the magnetrc flux from said electromagnet t ereby leavmg a relatively small portion of the magnetic flux to assume a path across the composite airgap between said V-shaped portion and said stop.

15. A current-sensing relay as set forth in claim 1 that ina second contact mounted from said housing, disposed on the opposite side of said blade from said first contact, and in engageable alignment with said movable contact.

16. A current-sensing relay as set forth in claim 1 that ineludes:

an auxiliary plug terminal mounted on said housing and connected in circuit electrical actuator for connection to a lead from an auxiliary actuator whereby said relay may be actuated by said auxiliary actuator.

Claims

1. A current-sensing relay for operating in response to a predetermined electric current in a lead, said relay comprising: a housing including a ferromagnetic loop formed with a ferromagnetic bar; a first contact mounted on said housing; a movable contact disposed in engageable alignment with said first contact; a blade carrying said movable contact; electrical actuator means for moving said blade to selectively engage and disengage said contacts; sensiNg coil means wound on said bar and mounted in circuit with said actuator means for sensing the current in said lead and responsive to said predetermined electrical current to produce an electrical signal; amplifier means in circuit with said actuator means and sensing means and responsive to said signal to operate said actuator means and move said blade whereby said relay will operate in response to said predetermined electrical current.

2. A current-sensing relay as set forth in claim 1 wherein: said blade is elongated, flexible and crooked and has one end affixed to said housing and carries said movable contact on its free end; and said actuator means operatively engages said blade intermediate said one end and said movable contact to move said free end transversely and engage said movable contact with said first contact, and then continue transverse movement of the intermediate portion of said blade to further flex said blade and slide said movable contact across said first contact a sliding distance greater than it would be slid by an equivalent amount of transverse movement of the intermediate portion of a straight blade whereby when said actuator is released said blade will unflex and move said movable contact said sliding distance across said first contact to provide a relatively large contact breaking force.

3. A current-sensing relay as set forth in claim 1 wherein: said amplifier means includes a silicon-controlled rectifier having its gate in circuit with said sensing means and its power circuit in circuit with said actuator means.

4. A current-sensing relay as set forth in claim 1 wherein: said actuator means includes an arm having its front extremity projecting over said blade for engagement therewith, a mount carried on said housing for supporting the rear extremity of said arm and including a resilient holding clip projecting forwardly over the rear extremity of said arm and beyond said mount to bias said front extremity downwardly toward said blade.

5. A current-sensing relay as set forth in claim 1 wherein: said housing includes a terminal receiving passage formed with a depression in one side for defining a keyway; and said relay includes a plug terminal in circuit with one of said contacts and projecting through said passage to form a plug prong, said terminal being formed with a reduced-in-cross-section portion defining a key for complimentally interfitting said keyway whereby said terminal may be inserted in said passage, shifted laterally therein to fit said key in said keyway, and affixed to said housing to mount said terminal firmly on said housing.

6. A current-sensing relay as set forth in claim 1 wherein: said housing is formed with a terminal receiving passage; and said relay includes a terminal for insertion in said passage and including a malleable rivet forming portion whereby said terminal may be inserted in said passage and said rivet forming portion riveted over to hold said terminal captive in said passage.

7. A current-sensing relay as set forth in claim 1 wherein: said housing includes a base formed with a pair of oppositely disposed sidewalls formed on their exterior with respective clip-receiving recesses, said housing further including a cover formed with a pair of oppositely disposed downwardly projecting sidewalls in juxtaposition with the walls of said base and formed with resilient clips for receipt in said recesses to lock said cover to said base.

8. A current-sensing relay as set forth in claim 1 wherein: said housing includes a blade mount; said actuator includes an arm formed on its rear extremity with a pair of spaced apart legs carried on said mount, and is formed intermediately with a downwardly projecting apex; and said housing includes a stop disposed adjacent said apex for engagement thereby to limit travel of said arm toward its contact closing position whereby said arm will be supported at three points when said relay is actuated.

9. A current-sensing relay as set forth in claim 1 that includes: a bobbin formed with a spool for winding said coil thereon and with a passage extending through the center of such spool for receipt of a magnetic conductor disposed in electrical inductive relationship with said lead.

10. A current-sensing relay as set forth in claim 2 wherein: said blade is formed intermediately with a peg-receiving opening; and said actuator means includes a peg which loosely interfits said opening whereby the intermediate portion of said blade will be free to shift forwardly and rearwardly during actuation of said relay to facilitate alignment between said blade and actuator.

11. A current-sensing relay as set forth in claim 1 wherein: said housing includes a mounting bar having its opposite ends connected with said loop and having said coil wound therearound.

12. A current-sensing relay as set forth in claim 11 wherein: said housing is formed with a pair of slots for receiving the opposite extremities of said loop; said loop is generally U-shaped and has its opposite extremities projecting through said slots and said opposite extremities are formed with openings; and the opposite extremities of said mounting bar project through said openings and are secured to said housing to affix said loop to said housing.

13. A current-sensing relay as set forth in claim 9 wherein: said actuator means includes a plurality of electrical components; and said bobbin includes a plurality of holding tabs forming cavities for receipt of said respective components.

14. An electrical switch as set forth in claim 1 wherein: said actuator means includes an electromagnet having its core formed on one end with a stop, an arm coupled with said blade and overlying said core and formed with a V-shaped ferromagnetic portion disposed adjacent said stop and having its apex engageable therewith when said electromagnet is energized whereby said V-shaped portion will form a plate for a relatively large portion of the magnetic flux from said electromagnet thereby leaving a relatively small portion of the magnetic flux to assume a path across the composite airgap between said V-shaped portion and said stop.

15. A current-sensing relay as set forth in claim 1 that includes: a second contact mounted from said housing, disposed on the opposite side of said blade from said first contact, and in engageable alignment with said movable contact.

16. A current-sensing relay as set forth in claim 1 that includes: an auxiliary plug terminal mounted on said housing and connected in circuit electrical actuator for connection to a lead from an auxiliary actuator whereby said relay may be actuated by said auxiliary actuator.