US2743326A

US2743326A - Switch for overload protecting circuits

Info

Publication number: US2743326A
Application number: US332247A
Authority: US
Inventors: Lynn H Matthias
Original assignee: Allen Bradley Co LLC
Current assignee: Allen Bradley Co LLC
Priority date: 1953-01-21
Filing date: 1953-01-21
Publication date: 1956-04-24
Anticipated expiration: 1973-04-24

Description

April 24, 1%956 L. H. MATTHIAS SWITCH FOR OVERLOAD PROTECTING CIRCUITS Filed Jan. 21, 1953 5 Sheets-Sheet 1 Z Tn-E E Ls Z2 /6 I, 45 Z 3 INVENTOR.

X/7M4 F g. am/4M April 24, 1956 L, H. MATTHIAS 2,743,326

SWITCH FOR OVERLOAD PROTECTING CIRCUITS Filed Jan. 21, 1953 3 Sheets-Sheet 2 F-Z-g. 5 7 A? I I" 25 Z/ 1N VEN TOR.

April 24, 1956 l s 2,743,326

SWITCH FOR OVERLOAD PROTECTING CIRCUITS Filed Jan. 21, l93 3 Sheets-Sheet 5 IN V EN TOR.

BY 1; A1 k Gww (42% %M United States Patent 0 2,7 3,32 SWITCH FOR OVERLOAD PROTECTING cmcurrs Lynn H. Matthias, Fox Point, Wis., assignor to Allen- B adl y ompany i w ukee Wis, a correlation of Wis n Application January 21, 1953, Serial No. 332,247

6 Claims. c1. goo- 1 24 This invention relates to protective switches for incorporation in overload protecting circuits such as are employed in conjunction with electric power circuits and it more particularly resides in a switch having a trip member mounted for movement between a contact opening position and a cocked position where it is retained tween the contact member and the trip member to ,act

upon the trip member to return it to cocked position while retaining the movable contact member in open position.

A common usefor protective switches, sometimes called protective relays, is in conjunction with motor starting controls, wherein means responsive to load conditions in the motor load circuit act upon contacts in a control circuit that in turn acts to close or open the line contactors of the motor load circuit. The invention herein set forth is, among other uses, adapted for employment as a protective relay in such motor controlling apparatus. It is desirable in such a protective relay to provide so called pr e pr p r i t is o s p op tie w i h P h the retention of the relay contacts in closed position if and so long as an overload condition persists. It is common to employ in protective relays a resetting member that acts in one direction of movement to reset the automati pp n l m n d o mo the c n a baqk int en e e la f h type, w ich are ommon y employed, do not incorporate trip-free features. Where the trip-free function is provided, it has heretofore been usual to execute a resetting operation wherein the tripping mechanism is returned to cocked position and the switch is prepared to move the contacts closed while maintaining the contacts open, and to thereafter execute a closing operation which brings about closure of the contacts. Such structures are complex and expensive.

It is an object of this invention to provide a simplified protective switch wherein the contacts cannot be retained in lose Pos tio if an a ss s an ovs ls d exists in the circuit to be protected. Y

It is another object o fthis invention to provide a protective switch having a reset member which normally dwells in the set position and which is operable in one motion to reset the automatic trip elements and place the switch in condition to urge the contacts into closed position, while maintaining the contacts in an open position until the reset member is allowed to return from resetting position.

It is another object of this invention to provide a protective switch in which operating "forces for movement arrrip member be ween sonar opening posi ion an in a in an a more than s ashe which the trip member in turn moves to contact open position.

It is another object of this invention to provide a protective switch accomplishing the foregoing objects with only three coacting movable elements of rugged compact construction.

These and. other objects and advantages will appear in the description to follow. In the description, reference is made to the accompanying drawings, in which there is shown by way of illustration and not of limitation a specific form in which this invention may be embodied.

In the drawings:

Fig. l is a rear view in elevation with parts broken away and in section of a thermally actuated overload relay including an insulating mount therefore in which this invention is embodied,

Fig. 2 is a plan view of the overload relay shown in Fig. 1,

Fig. 3 is a front view in elevation of the overload relay detached from the mount with parts in closed position, Figure 4 is a fragmentary plan view with parts in section of the overload relay viewed through the plane 4-4, shown in Fig. 3,

Fig. 5 is a fragmentary front view in elevation with parts removed of the overload relay showing switch elements in tripped position,

Fig. 6 is a fragmentary front view in elevation with parts broken away of the overload relay showing the switch elements in resetting position preparatory to reiesi n Fig. 7 is a view in perspective of a thermally responsive spindle and ratchet assembly that forms a part of the overload relay.

Referring now to the drawings, there is shown in Figs. 1 and 2 a mount 1 preferably formed of a durable dielectric molding material such as phenol-aldehyde or other resin in which a relay constructed in accordance with this invention may be mounted. Extending downwardly from the mount 1 are attachment bolts 2 for suitable attachment to a panel-board, or the like, to which the apparatus is to be afiixed. Embedded in the mount 1 is a pair of terminal studs 3 which project upwardly from the top face of the mount 1 to form suitable connectors for terminal lugs of conductors in a load circuit to be protected.

The mount 1 is recessed at the rear of its mid-section to receive a "relay case 4, formed preferably of phenolaldehyde or other resin having requisite strength and insulating properties. A'pair of conducting terminal strips 5 are securely attached to the upper face of the relay case 4 by bolts 6, as shown in Fig. 3. The terminal strips 5 extend laterally from the relay case 4, overlap the mount 1 and encircle the terminal studs 3 to provide suitable connections with load circuit connector lugs, not shown, but intended to be secured by studs 3. The strips 5 are secured to the mount 1 by means of mounting screws 6, which are shown in Fig. 2, thus holding the relay case 4 firmly in place.

The automatic opening of the overload relay shown and described herein is dependent upon a heat responsive spindle assembly 7 which is shown in detail in Fig. 7. The spindle assembly 7 has a hexagonal base 8 adapted to be received in a complementary recess in the upper face of the relay case 4. Attached to the base 8 is a hollow sleeve 9 which passes through the base 8 and forms a bearing for a releasable catch in the form of a ratchet wheel lit. The ratchet wheel in is normally restrained from rotation with respect to the sleeve 9 by a film of fusible alloy, such as an eutectic solder occupying the clearance between the ratchet l9 and sleeve 9. Upon fusion of the solder, caused by eating, the ratchet wheel it) is freed to rotate inresponse to a tangentially applied force. To retain the spindle assembly 7 in posiside and thence downwardly along the sleeve 9 to provide for. effective heat transfer from the'heater 13 tothe sleeve 9.' The strip heater 13 is proportioned to cause response to a' predetermined overload condition in the circuit to be protected, This response takes place when an overload current passing through the heater 13 causes a temperature rise inthesleeve 9 suflicient to fuse the solder normally restraining'the ratchet wheel 19 from rotation. Release of ratchet permits the opening of switch elements to be hereinafter described. 7

The rear of the relay case 4 is closed by a removable 7 cover 15 held in place by'screws 16. In Fig. l the cover 15 is shown broken away to expose a vertically mounted reset lever 17 slidingly received in a recessed track formed as a part of the vertical wall 18 of the case 4. A spring 19 disposed beneath the lever 17 urges the same upwardly which upward movement is arrested by a shaft 20 which passes through and strikes the upper margin of an opening 21 in the vertical wall 18. A pair of

terminals

22 and 23 located on the back of the relay case 4 extend through the wall 18 to provide a pair of

stationary contacts

24 and 25 adjacent one another at the front of the relay.

Projecting forwardly from the vertical wall 18 is a horizontal pivot shaft 26 upon which is mounted a roughly triangularly shaped trip member 27. The upper vertex of the trip member 27 has fixed thereto a latch pawl 28 having a rearwardly turned lip 29 which engages ratchet 10 when the trip member 27 is swung clockwise about the shaft 26 to a position such as is shown in Figs. 3 and 6. Upon engagement of the lip 29 of the pawl 28 with the ratchet 10 thetrip member 27 is restrained from counter-clockwise movement unless the spindle solder is in a molten state. Herein the trip member 27 is said to be held in a cocked position when the pawl 28 is engaged with the ratchet 10, and the ratchet 10 is non-rotatable because of solidification of said solder. When the solder is molten and the pawl 28 is released from the ratchet 10 to permit counter-clockwise movement of the trip member 27 the trip member 27 is said to be tripped.

A movable contact arm 31, attached by a displaceable pivotal connection 30 to the base corner of the trip member 27 on theside of the shaft 26 opposite from the

contacts

24 and 25, carries a central hump that forms a spring seat 32 disposed above the pivot shaft 26 and beneath the reset lever shaft 20. From the hump portion, contact arm 31 extends toward the left past the pivot shaft 26 and thence downwardly to provide a mounting for a movable bridging contact 33 disposed in facing relation to the

stationary contacts

24 and 25. The bridging contact 33 is pivotally mounted on the arm 31 to ensure proper engagement with the

stationary contacts

24 and 25. Projecting forwardly from the pivotal mounting of contact 33 is a stud 34 that extends beneath the tripmember 27 across the path of downward movement thereof, to be moved thereby. Downward travel of the contact arm 31 is limited by a ledge 35 which extends forwardly from the vertical wall 18 into the path of a fulcrum toe 36 at the end of the contact arm 31. A bias spring 37 inserted between a bottom ledge 38 of the relay case 4 and the spring seat 32 on the underside of the contact arm 31 applies a counter-clockwise moment to the parts pivoting about shaft 26 and a clockwise moment to the parts pivoting about the connection 30.

An instance illustrative of a use for which the apparatus is suited would be one in which the terminal strips 5 are connected in a load circuit to be protected and the

terminals

22 and 23 are connected in a control circuit adapted to open a load contactor in the load circuit upon opening the bridging contact 33. The relay in that case would be set as in Fig. 3 with the bridging contact 33 held in closed position and the trip member 27 retained in cocked position. Upon occurrence of an overload in the load circuit, such as to cause fusion of the solder retaining the ratchet wheel 10, the contact 33 will be thrown to open position. The opening movement is initiated by tripping the trip member 27 with a release of the pawl 28 followed by counter-clockwise rotation of trip member 27 about its pivotal mounting 26. This motion moves the floating pivot 30 upward and is accompaniedrby a rotation of the trip member 27 to= ward and into engagement with the stud 34. Trip mem ber 27 upon engaging stud 34 picks up the contact arm 31 and moves it as a unit with member 27 about the pivot shaft 26 to carry the bridging contact 33 away from the

contacts

24 and 25. Movement in this direction is arrested upon engagement of the fulcrum toe 36 with the ledge 35 of the relay case 4. The elements of the relay then come to rest in the position shown in Fig. 5.

To reset the contacts in closed position the reset lever 17 is moved downwardly against its associated spring 19 'thus moving the shaft 20 against the movable contact arm 31. This movement causes the movable contact arm 31 to be swung about the fulcrum toe 35 to cause a com pression of the bias spring 37 and a lowering of the floating pivot 30. Movement of the pivot 30 rotates the trip member 27 about the pivot shaft 26 to cocked position in which the pawl 28 engages with the ratchet wheel 10. The positions of the relay elements, upon thus moving the reset lever 17 to its downward position are shown in Fig. 6. If the fusible solder between the ratchet 10 and the stud 9 is in a solid state prohibiting rotation of the ratchet 10 the trip member 27 will be retained in the position shown in Fig. 6 upon release of the lever 17. Release of the reset lever 17 under such conditions permits the bias spring 37 to rotate the movable contact arm 31 about the floating pivot connection 30 thus bringing the bridging contact 33 into bridging relation with the

contacts

24 and 25 to return the relay to the position of Fig. 3.

In resetting the apparatus the movable contact 33 is retained in open position until the reset lever 17 is released. If, upon an attempt to reset, the solder between the ratchet 10 and stud 9 is in a fused state release of the reset lever 17 will be accompanied by a swinging movement of the, trip member 27 back to contact opening position. The contact arm 31 is thus retained in contact open position. If the solder retains the ratchet 10 in a fixed position release of the reset lever 17 will allow the contacts to close. An overload condition, if still persisting, will again cause the solder to fuse and the contacts will again be opened regardless of any manipulation of reset lever 17. There is thus provided a protective switch in which the contacts cannot be retained in closed position if an overload condition is present in the circuit to be protected.

I claim:

1. In a protective switch the combination comprising a contact opening trip member mounted for movement to and from a contact opening position and a cocked position, a releasable catch engageable with said trip member adapted to retain said trip member in cocked position when moved to that position and to releasably trip said trip member to permit movement thereof to contact opening position, fixed electrical contact means, an arresting abutment, a contact arm borne by said trip member having a movable electrical contact and movable between a closed position in engagement with said fixed contact means and an open position wherein said contact arm rests against said abutment, said contact arm being disposed in the path of movement of a portion of said trip member to b str ck ndca isd h reb to said Qn PQ R 499 o men f ai n m mb 9 sea n P tion, bias means engaging sat contact urging. the same toward closed position when said trip member is in cocked P s tion. and a e. a aid n est arm to apply a force to said trip member ourge thelatter toward contact opening position when tripped, and reset means positioned to apply a force to said contact arm to move the same against said bias means and to move said trip member when tripped to cocked position while retaining said contact arm in open position.

2. In a protective switch the combination comprising a releasable catch, a trip member movable in one direction to a contact opening position and movable in another direction to. a cocked position, a latch fixed to, said trip member engageable with said catch upon movement of said trip member to said cocked position to retain said trip member in the cocked position, stationary elec trical contact means, a fixed abutment, a contact arm borne by said trip member with a displaceable connection that provides relative movement between the contact arm and the trip member and extending from the displaceable connection to form a contact mounting and to be disposed in spaced facing relation to said abutment, said contact arm being disposed in the path of movement of a portion of said trip member to be struck and carried thereby toward said abutment, movable electrical means on said contact mounting in facing relation to said stationary contact means movable to closed position therewith upon movement of said arresting portion from said abutment and movable to open position therewith upon movement of said arresting portion toward said abutment, and resilient bias means cooperatively engaged with said contact arm urging said arm away from said abutment to carry said movable contact means into closed position when said trip member is in cocked position and to urge said contact arm about said fixed contact when said contact means are closed to move said displaceable connection and hence said trip member toward contact opening position to strike said contact arm and carry the same toward said abutment.

3. in a protective switch the combination comprising a releasable catch, a pivota'lly mounted contact opening trip member including a floating pivot connection disposed to one side of the pivotal mount of the trip member, movable in one direction of rotation to a contact opening position and movable in the opposite direction to a cocked position, a latch forming a part of said trip member engageable with said catch upon rotation of said trip member to said cocked position to retain said trip member in the cocked position, stationary electrical contact means, a fixed abutment, a contact arm joined to said floating pivot connection extending from the floating pivot connection past and to the opposite side of the pivotal mounting of said trip member to form a fulcrum in facing relation to said fixed abutment, movable electrical contact means mounted on said contact arm in facing relation to said stationary contact means movable to closed position upon movement of said fulcrum from said abutment and movable to open position upon movement of said fulcrum toward said abutment, a shoulder formed as a part of said contact arm disposed to be struck by said trip member upon movement to said contact opening position, resilient bias means cooperatively engaged with said contact arm urging said arm about said floating pivot connection to carry said movable contact means into closed position and urging said contact arm upon a release of said latch that permits displacement of said pivotal connection to pivot about said fixed contact means to move said floating connection and hence said trip member toward contact opening position whereby said trip member engages said shoulder of said contact arm and carries said contact arm to engage said fulcrum with said abutment, and an operating lever engageable with said contact arm at a point between said fulcrum and the. n a em n h sa d e ie t a means m rable to displace said cdnta ct arm against saidbias" means" I 4, In a protective switch the combinationcornprising a mounting case, a heat'rdsponsive catch carried by said mounting, a heater disposed heating relation to said catch adapted to be connected in a load circuit, a trip member pivotally mounted on said mounting case rotatable in one direction to'a contact opening'position and rotatable in the opposite direction to steere position, a latch on sa f trip member ei igafgeable. with saidcatchto retain said nip nienifber incocked position when moved to that position, said latch being releasable from en: gagement with said catch upon heating of said catch, a stationarycontact fixed to said mounting case, an abut m ent forminga part of said mounting case, a contact arm pivotally connected by a floating'pivot' to said trip mem her which floating pivot is disposed to rotate about the pivot of said trip member upon rotation of said trip member, said contact arm having a fulcrum in facing relation to said abutment and a movable contact in facing relation to said fixed contact and being movable between a position of contact engagement and a position engaging said fulcrum with said abutment, a bias spring fixed at one end to said mounting case and cooperatively engaged at the opposite end to said contact arm urging said contact arm when said latch is engaged with said catch member toward said position of contact engagement and urging said contact arm upon release of said latch to pivot about the engaging contacts to move the floating pivot and hence rotate said trip member to pick up said cont-act arm to swing said contact arm to engage said fulcrum with said abutment, and an operating lever engageable with said contact arm at a point between said fulcrum and the engagement with said spring movable to displace said contact arm about said fulcrum when in engagement with said abutment to move the floating pivot for rotation of said trip member to said cocked position.

5. in a protective switch the combination comprising a releasable catch, a contact opening trip member movable in one direction to a contact opening position and movable in an opposite direction to a cocked position, a latch forming part of said trip member engageable with said catch to retain said trip member in cocked position when moved to that position, stationary electrical contact means, a contact arm borne by and movable with respect to said trip member having a portion in the path of movement of said trip member to be struck thereby upon movement thereof to contact opening position, a movable electrical contact mounted on said contact arm movable to closed position with said stationary contact means and movable to open position therewith upon movement of said trip member to contact opening position, and bias means acting upon said contact arm acting to move said contact arm and said trip member as a unit upon release of said latch whereby said movable contact is moved to open position and to move said contact arm in the opposite direction to cause contact closure when said trip member is in cocked position, and reset means cooperating with said trip member and contact arm to move said trip member to cocked position while restraining said contact arm in contact open position.

6. In a protective switch the combination comprising a releasable catch contact opening trip member pivotally mounted on a stationary pivot including a floating pivot disposed radially away from the pivot center of its mounting, said trip member being rotatable in one direction to a contact opening position and rotatable in the opposite direction to a cocked position, a latch forming a part of said trip member engageable with said catch to retain said trip member in said cocked position when moved to that position, stationary electrical contact means, a contact arm joined to said trip member at said floating pivot and extending therefrom toward and beyond the stationary pivot forming the mounting for said trip member and terminating in a fulcrum end, a fixed amasae abutment positioned to. be engaged by said fulcrum end,

7 a movable electrical contact mounted on said contact arm in facing relation to said stationary electrical contact means movable to a closed position upon movement of said fulcrum from said abutment and movable to an open position upon movement of said fulcrum into engagement with said abutment, bias means acting upon said contact arm acting to rotate said contact arm and said trip member as a unit upon release of said latch from said catch whereby said fulcrum end is engaged with said abutment and to rotate said contact in the opposite direction upon retention of said trip member in cocked position, and a reset lever engageable with said contact arm at a point between said fulcrum end and the engagement with said bias means adapted to move said References Cited in the file of this patent UNITED STATES PATENTS 1,978,731 Wilms Oct. 30, 1934 2,001,559 Wilrns May 14, 1935 2,385,727 Platz Sept. 25, 1945 2,496,020 Pepper Jan. 31, 1950 2,532,265 Zickrick Nov. 28, 1950 2,597,068 Cobb May 20, 1952 2,626,330 1953 Harrold Jan. 20,