US3147351A

US3147351A - Trip free overload relay

Info

Publication number: US3147351A
Application number: US77696A
Authority: US
Inventors: Karl A Brandenberg
Original assignee: Square D Co
Current assignee: Schneider Electric USA Inc
Priority date: 1960-12-22
Filing date: 1960-12-22
Publication date: 1964-09-01
Anticipated expiration: 1981-09-01
Also published as: GB998276A

Description

P 1, 1964 K. A. BRANDENBERG 3,147,351

' TRIP FREE OVERLOAD RELAY 2 Sheets-Sheet 1 Filed Dec. 22, 1960 INVENTOR.

KAZL A. BPANDENBEEG BY Sept. 1, 1964 K A. BRANDENBERG 3,147,351

- TRIP FREE OVERLOAD RELAY Filed Dec. 22, 1960 V 2 Sheets-Sheet 2 e e v a d: 5

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United States Patent 3,147,351 "ram FREE OVERLOAD RELAY auras: Patented Sept. 1, 1964 Ice I its tripped position, to pivot the contact operating arm Karl A. Brandenberg, Hayward, Calif., assignor to Square 1) Company, Park Ridge, 111., a corporation of Michigan Filed Dec. 22., 1960, Ser. No. 77,696 It) Claims. (Cl. 2129-416) This invention relates generally to electrical overload responsive devices and more particularly to an improved electrical overload relay that is trip-free.

Many types of overload relays are in use for effecting interruption of an electric circuit automatically when the circuit becomes overloaded or a short circuit occurs. Usually such relays include a thermal or magnetic responsive mechanism operative, upon an overload or fault in a main circuit being protected, to move a latch thereby to release a movable contact of a pair of closed separable contacts for quick interruption of a pilot circuit. A means responsive to the interruption of the pilot circuit opens the main circuit.

An overload relay generally includes means for promptly and safely restoring the separable contacts to their normal closed position and for resetting the contact operating mechanism to its normal or untripped position. In order for the relay to be trip-free, the restoring or resetting mechanism must be so arranged that it is impossible by manipulation of the resetting mechanism to prevent opening of the relay contacts under overload conditions. Further, it is desirable that the resetting mechanism be operable at any time and in any manner without preventing the contacts from opening and, if opened, without causing them to close unless the overload has had time to subside. Many of the prior relays lack simple and conveniently manipulable resetting mechanisms having these advantages and many have intricate and sensitive contact operating mechanisms which are difficult to assemble and require frequent adjustment.

Accordingly, an object of this invention is to provide an improved overload responsive relay which is always trip-free regardless of how or when the reset mechanism is manipulated and wherein the above mentioned objectionable features are eliminated.

Another object of ithe invention is to provide an improved overload responsive relay of simple construction which cannot be prevented from opening, cannot be held closed under overload conditions, and cannot be damaged or abused by improper manipulation of the reset mechanism.

It is another object of my invention to provide an improved overload responsive relay in which the contacts cannot be held closed inadvertently or intentionally when an overload exists.

It is another object to provide an improved overload responsive relay in which the contacts are held open until the rest mechanism is released after its initial resetting movement.

Still another object is to provide an improved overload responsive relay which is compact and durable and in which all parts are normally concealed and protected although being readily accessible for inspection and replacement.

An overload relay in accordance with this invention comprises a releasable member, a contact operating arm pivoted on the releasable member, a biasing means for the member and said arm, and a current responsive latch holding said member against the bias of said biasing means. Upon release of the latch, the biasing means moves the releasable member rectilinearly to a tripped position. The biasing means becomes operative, consequent upon movement of the pivotal axis of the contact operating arm as the releasable member moves to into a tripped position. For resetting the relay, a reset means is movable to engage the contact operating arm to return the releasable member to its latched position. When the releasable member returns to its latched posi-' tion, the pivotal axis of the contact arm is positioned so that the biasing means returns the contact arm to its initial or untripped position. So long as the contact arm is in its untripped position, it cannot be engaged by the reset means. Hence, manipulation of the reset means is of no effect when the contact arm is in its untripped position.

Other objects and advantages of the invention will be apparent from the following description, wherein reference is made to the drawings, in which:

FIG. 1 is a wiring diagram showing how an overload responsive relay in accordance with this invention can be used to protect an electrical load;

FIG. 2 is a perspective view of an overload responsive relay in accordance with this invention;

FIG. 3 is a side view of the relay of FIG. 2 with a housing part removed and the operating mechanism shown in its normal position to permit energization of the load to be protected.

FIG. 4 is a sectional view taken generally along the line 44 of FIG. 3;

FIG. 5 is an exploded view of the operating mechanism of the device;

FIG. 6 is a side view similar to FIG. 4 with the operating mechanism of the relay in a position to prevent energization of the load;

FIG. 7 is a side view similar to FIG. 4 with the mechanism in its position just prior to being reset.

Referring first to FIG. 1, there is shown an electric circuit including an electrical load such as a motor 18 connected across a source of power, represented by the conductors Ll-LZ, in series with a heating unit 19 of an overload responsive relay which includes a double-throw switch member 20 arranged to connect to the source of power L1-L2 either an operating coil 21w of an electromagnetic switch 21 or an alarm circuit which includes, for example, a bell 22.

The circuit of FIG. 1 is rendered operative by closing a manual switch S thereby to complete a circuit from the source of power L1-L2 to the coil 21w through the switch 20 which normally is in an upper position as shown. Energization of the coil 21w causes normally open contacts 21a of the switch 21 to connect the motor 18 and the heating unit 19 in series with each other across the source of power. When an overload or short circuit condition occurs in the circuit including the motor 18, the heating unit 19 responds to cause the switch member 20 to move to its lower position to complete the circuit from the power source through the bell 22 and, at the same time, by moving from its upper position, to deenergize the circuit including the coil 21w which, in turn, results in opening of the contacts 21a and disconnection of the motor 18 and the heating unit 19 from the source of power.

Referring now to FIG. 2, an overload responsive relay in accordance with this invention is illustrated as including an overload responsive assembly 23 comprising the heating unit 19, a solder pot 24, and a ratchet Wheel 25. The assembly 23 is fastened in bridging relation to and between a pair of electrically

conductive supports

26 and 27 by mounting

screws

28 and 29. The combination of the overload responsive assembly 23 and the

supports

26 and 27 to which it is secured is, in turn, aflixed to an upper surface of an insulating mounting base 30 by a pair of screws (not shown) which pass through respective openings extending through the base 30 from the bottom thereof and thread into respective openings formed in the lower portions of the

supports

26 and 27.

Suitable terminals

31 and 32 are provided on the

supports

26 and 27, respectively, so that the heating unit 19 may be electrically connected in series with a load as shown in the wiring diagram of FIG. 1. The ratchet wheel 25, as shown most clearly in FIG. 4, is non-rotatably secured to an outer end portion of a shank 25a which has its inner end portion extending into the solder pct 24.

Under conditions of normal current flow in a circuit including the heating unit 19, the solder in the pot 24 remains solid and holds the shank 25a and the ratchet wheel 25 against rotation. The melting point of the solder is such that it will melt and release the shank 25a and the ratchet wheel 25 for rotation only when it is heated by a current above a predetermined value flowing through the heating unit 19.

The construction and operation of such an overload responsive assembly 23 is old in the art and is fully disclosed in Van Valkenburg Patent No. 1,752,5l4. It will become apparent that other types of overload responsive assemblies from that shown may be used as desired.

A reset mechanism or slider 33 in the form of a rectangular frame and preferably molded from a strong plastic material extends outwardly from an enclosure carried by the base 30 and formed of juxtaposed molded

insulating parts

34 and 35 which define a housing for a switch mechanism.

Referring now particularly to FIG. 3, movement of the slider 33 is limited to linear reciprocating motion in the direction of its major length by the coaction of the slider with spaced apart guide surfaces 36 defined by inwardly directed projections on the

parts

34 and 35. The upper limit of travel of the slider 33 is determined by engagement of a projecting stop 37 on the slider 33 with a downwardly directed shoulder 38 formed on the enclosure part 34. The

parts

34 and 35 are held together by suitable fastening means 39 received in respective pairs of aligned holes 39a and are fastened to the mounting base 30 by a pair of suitable screws (not shown) received in respective pairs of aligned holds 40. A sheet 41 of insulating material (shown most clearly in FIG. 2) may be disposed between the enclousre part 35 and the base 30.

The switch mechanism includes a double-faced contact 44 carried by and electrically connected to the upper end portion of an elongated flexible leaf spring contact arm 45 which corresponds to the switch of FIG. 1. The arm 45 has its lower end portion bent into a U-shape, the shorter leg 45a of which is clamped between an inner leg 46a of a terminal member 46 and a tongue 46b pressed from the inner leg 46a. The terminal 46 extends through a slot formed in sidewalls of the

parts

34 and 35 and receives a wire-holding screw 47 in its outer leg.

The contact 44 on the switch arm 45 is movable between a stationary alarm circuit contact 50 and a stationary control circuit contact 51 secured, respectively, to inner leg portions of

terminal members

54 and 55 which extend through respective slots defined in the sidewalls of the

housing parts

34 and 35 and receive wire-

holding screws

56 and 57, respectively, in their outer leg portions. With the switch arm 45 in the normal position of FIG. 3, a circuit is completed from the terminal member 55 through the contacts 51 and 44 and thence through the switch arm 45 to the terminal member 46 to permit energization of a load such as the motor 18. When the overload relay is tripped upon occurrence of an overload, as will be described, the switch arm 45 is released so that the contacts 51 and 44 separate and the contact 44 assumes a new position, shown in FIGS. 6 and 7, in engagement with the alarm circuit contact 50 to complete an alarm circuit through the

terminal members

46 and 54.

In accordance with this invention, the position of the switch, arm 45 and its associated contact 44 is determined by a lower arm 58 of a two-armed, pivoted contact operating lever or member 60 formed of insulating material such as nylon and having an upper arm 59. A two-armed pivoted latching lever or releasable means 61 having a lower arm 62 has a pawl 64 formed on its upper arm 63 which is normally in engagement with one of the teeth of the ratchet wheel 25 when the overload relay is in its normal untripped position, as shown in FIG. 3.

The operating member 60 is rotatably received on an annular boss 61a formed on the latching lever 61. A pin 65 fixedly held in the opening in the boss 61a is free to rotate and to slide in a vertically directed recess or track 66 (shown most clearly in FIG. 7) formed in the enclosure part 35.

An L-shaped leaf spring 67 received in a recess defined by projections on the

enclosure parts

34 and 35 acts on one side of the lower arm 62 of the releasable means or lever 61 to constantly urge the lever 61 in a clockwise direction so that the pawl 64 on its upper arm 63 can operatively engage the ratchet wheel 25 while a helical compression spring 68 received between spaced upstanding projections 69 on the housing part 34 constantly engages the operating member 66 at a projection 70 which it surrounds to bias the member 60 in a clockwise direction or counterclockwise direction as will be explained. The reset slider 33 is constantly biased outwardly and upwardly by a helical compression spring 71 acting between a lower wall defined by the

housing parts

34 and 35 and a shoulder 72 defined by the base of a semi-cylindrical, spring-receiving groove in the slider 33. An upwardly directed surface 74 at the end of the arm 59 of the operating member 60 is engaged by a shoulder 75 on the slider 33 (shown most clearly in FIGS. 5 and 6) when the slider 33 is depressed for resetting the switch mechanism after it has been tripped. The relative positions and, coaction of the slider 33, the operating member 60, the latching lever 61, and the ratchet wheel 25 with one another as described above are clearly shown in exploded relation in FIG. 5.

Further understanding of the invention will be had from the following description of the operation of the relay. Assuming the relay to be in the tripped position shown in FIG. 6 with the contacts 44 and 50 in engagement to complete the alarm circuit and the slider 33 in its uppermost or outer position, moving the slider 33 downwardly against the force of the spring 71 causes the shoulder 75 on the slider 33 to engage the surface 74 on the operating member 60, thereby to move the member 60, the lever 61, and the pivot pin 65 downwardly against the bias of the spring 68. During this downward movement, the pawl 64 on the lever 61 freely passes the ratchet wheel 25 and at the lower limit of movement reaches a position in which the pawl 64 is below the ratchet wheel 25 as shown in FIG. 7. As long as the slider 33 is held in this position, the engagement of the shoulder 75 and the surface 74 prevents the operating member 60 from rotating counterclockwise about the boss 61a, even though urged to do so by the bias of the spring 68, and thereby prevents the arm 58 from moving the contact arm 45 and its movable contact 44 counterclockwise.

Upon slight release of the downward force on the slider 33, the bias of the spring 68 moves the lever 61 upwardly so that the pawl 64, because of the action of the spring 67, engages the teeth of the ratchet wheel 25. If the solder in the solder pot is cool, the ratchet Wheel 25- cannot turn and further upward movement of the pivotpin 65 in its track 66 is prevented. Because the shoulder 75 and the surface 74 are now disengaged, the spring 68 turns the operating member 60 in a clockwise direction about the axis of the pin 65. Thereupon, the de-. pending arm 58 of the member 60 strikes the contact arm 45 and drives its associated contact 44 out of engagement with the contact 50 and into engagement with the contact 51 to interrupt the circuit between the

terminals

46 and 54 and to complete a circuit between the

terminals

46 and 55. The relay is now in the position shown in FIG. 3.

If the solder in the solder pot 24 were not sufficiently.

cooled to'pi'event rotation of the ratchet wheel 25, release of the downward force on the slider 33 would permit the operating member 60 and the lever 61 to return to the position of FIG. 6 and the contact arm 45 would not be moved.

If the slider 33 should be depressed after the resetting operation has been completed and the parts are in the position of FIG. 3, the shoulder 75 does not engage the surface 74 of member 60 since the member 60 has pivoted in a.clockwise direction to a new position in which the surface 74 is out of the path of movement of the shoulder 75. Thus, the relay is trip-free. Whenever the ratchet wheel 30 is free to rotate upon overload conditions with the operating mechanism of the relay in the position of FIG. 3, the

levers

60 and 61 are free to move upwardly independently of the position of the slider 33 thereby to insure interruption of the load circuit in which the overload responsive relay is connected.

Whenever a current above a predetermined magnitude flows in the circuit including the heater 19, the solder contained in the solder pot 24 melts and the ratchet wheel 25 is permitted to rotate freely thereby to release the assembly including the lever 61, the pin 65, and the lever 60 for upward movement. During this upward movement, an upper edge 58a of the lower arm 58 of the lever 60 strikes a downwardly directed shoulder 76 formed by a projection on the housing part 35. Because of the bias of the spring 68, the member 60 pivots counterclockwise about the shoulder 76 as the spring 68 moves the pin 65 and the lever 61 upwardly from the position shown in FIG. 3 to the position shown in FIG. 6. This counterclockwise rotation of the member 60 causes its lower arm 58 to move out of engagement with the contact arm 45. Because of its resiliency, the contact arm 45 thereupon moves to the right and the circuit through the movable contact 44 and the stationary contact 51 is interrupted and the contact 44 engages the stationary contact 50 to complete the alarm circuit. After the solder has cooled, the relay may be reset, as explained above, for subsequent energization of the load.

What is claimed is:

1. An overload responsive relay comprising separable contacts, a first lever movable from a reset position holding said contacts closed into a tripped position permitting said contacts to be separated, a second lever movable independently of the first lever, a common pivot means for said first and second levers and movable in a fixed rectilinear path, a biasing means for said first and second levers, current responsive means normally restraining said second lever against the bias of said biasing means in a position such that said pivot means is at a first position in its rectilinear path of movement permitting said biasing means to bias said first lever to its reset position, said biasing means being operative upon release of said second lever by said current responsive means to move said pivot means in said rectilinear path to a second position permitting said biasing means to move said first lever from its reset position to its tripped position, and a reset mechanism including a plunger movable in a rectilinear path forireturning said pivot means from its second position to its first position thereby to permit said biasing means to return said first lever to its reset position.

2. A relay in accordance with claim 1 characterized in that said first lever is positioned in said rectilinear path of said plunger when the first lever is in said tripped position and is engageable by a portion of the plunger upon movement of said plunger in its path thereby to return said pivot means from its second position to its first position, and movement of said first lever from its tripped position to its reset position disposes said first lever out of said path of movement of said portion of the plunger.

3. A relay in accordance with claim 1 characterized in that said plunger has a portion thereon which is arranged 6 to engage said first lever only when said first lever is in said tripped position thereby to return said pivot means from its second position to its first position.

4. In a trip free overload relay, the combination comprising; a pivot movable in a rectilinear path in a housing for the relay, an actuating plunger having a portion externally accessible to the housing and an abutment carried by a portion of the plunger within the housing, said plunger being movable in the rectilinear path for moving the abutment in a rectilinear path in the housing; an actuating member rotatably carried by the pivot for movement between a reset position and a tripped position and movable with the pivot when the pivot moves in its rectilinear path, a switch member, said actuating member having a switch actuating portion engageable with said switch member when said actuating member is in the reset position and a second portion engageable with the abutment on the plunger only when said actuating member is in the tripped position, a releasable current responsive means having a latching member rotatably carried by the pivot and arranged to releasably maintain the pivot from movement from a first to a second position in its rectilinear path, a biasing means reacting on the switch actuating portion for rotatably urging the actuating member to the tripped position and the pivot to the second position in the rectilinear path, and a fixed abutment Within the housing engageable by the switch actuating portion of the actuating member when the pivot is in the second position in its rectilinear path for causing the biasing means to rotate the actuating member to the reset position wherein the switch actuating portion engages the switch member and the second portion is spaced from the path of movement of the abutment carried by the plunger.

5. The combination as recited in claim 4 wherein a single spring provides the bias to rotate the actuating member in one direction to the reset position and in the opposite direction to the tripped position.

6. The combination as recited in claim 4 wherein the current responsive means includes a melting alloy type overload element.

7. The combination as recited in claim 4 wherein the pivot is movable in a slot in the housing and the path of movement of the abutment on the plunger is parallel to the path of movement of the pivot.

8. In a trip free overload relay, the combination comprising; a pair of separable contacts, a pivot movable in a rectilinear path, a first lever rotatably mounted on the pivot for rotary movement between a reset position wherein the contacts are held closed and a tripped position wherein the contacts are separated, a second lever rotatably mounted on the pivot for rotary movement independently of the first lever, means biasing the first lever and pivot toward one position in the rectilinear path, releasable current responsive means engageable by the second lever for maintaining the pivot and second lever in a second position in the rectilinear path, an actuating plunger movable in a rectilinear path from an at-rest position to an actuating position, and mutually engageable portions on the first lever and plunger which are arranged for mutual engagement, only when the first lever is in the tripped position, for moving the first lever, the second lever and pivot from the first position to the second position as the plunger is moved from the at-rest position to the actuating position.

9. The combination as recited in claim 8 wherein the biasing means includes a single spring having one end in engagement with a portion of the first lever and the rectilinear path of movement for the pivot is defined by a pair of slots in a housing for the relay.

10. The combination as recited in claim 8 wherein the current responsive means includes a melting alloy type current responsive element.

(References on following page) References Cited in the file of this patent UNITED STATES PATENTS Wilms Feb. 9, 1932 Raney Oct. 18, 1938 Fisher Aug. 27, 1940 Jennings Sept. 10, 1940 Bierenfeld Sept. 16, 1947 8 Zickrick Nov. 28, 1950 Krieger Feb. 8, 1955 Blair Mar. 12, 1957 Locher Aug. 6, 1957 Kolb et a1. Nov. 19, 1957 Brackett Oct. 4, 1960 Wilcox et a1. Feb. 7, 1961 Furnas et a1. Feb. 21, 1961

Claims

1. AN OVERLOAD RESPONSIVE RELAY COMPRISING SEPARABLE CONTACTS, A FIRST LEVER MOVABLE FROM A RESET POSITION HOLDING SAID CONTACTS CLOSED INTO A TRIPPED POSITION PERMITTING SAID CONTACTS TO BE SEPARATED, A SECOND LEVER MOVABLE INDEPENDENTLY OF THE FIRST LEVER, A COMMON PIVOT MEANS FOR SAID FIRST AND SECOND LEVERS AND MOVABLE IN A FIXED RECTILINEAR PATH, A BIASING MEANS FOR SAID FIRST AND SECOND LEVERS, CURRENT RESPONSIVE MEANS NORMALLY RESTRAINING SAID SECOND LEVER AGAINST THE BIAS OF SAID BIASING MEANS IN A POSITION SUCH THAT SAID PIVOT MEANS IS AT A FIRST POSITION IN ITS RECTILINEAR PATH OF MOVEMENT PERMITTING SAID BIASING MEANS TO BIAS SAID FIRST LEVER TO ITS RESET POSITION, SAID BIASING MEANS BEING OPERATIVE UPON RELEASE OF SAID SECOND LEVER BY SAID CURRENT RESPONSIVE MEANS TO MOVE SAID PIVOT MEANS IN SAID RECTILINEAR PATH TO A SECOND POSITION PERMITTING SAID BIASING MEANS TO MOVE SAID FIRST LEVER FROM ITS RESET POSITION TO ITS TRIPPED POSITION, AND A RESET MECHANISM INCLUDING A PLUNGER MOVABLE IN A RECTILINEAR PATH FOR RETURNING SAID PIVOT MEANS FROM ITS SECOND POSITION TO ITS FIRST POSITION THEREBY TO PERMIT SAID BIASING MEANS TO RETURN SAID FIRST LEVER TO ITS RESET POSITION.