US3183328A

US3183328A - Electric switch with contact weld check means

Info

Publication number: US3183328A
Application number: US271294A
Authority: US
Inventors: Roy E Wheeler
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1963-04-08
Filing date: 1963-04-08
Publication date: 1965-05-11
Anticipated expiration: 1982-05-11

Description

May 11, 1965 R. E. WHEELER ELECTRIC SWITCH WITH CONTACT WELD CHECK MEANS Filed April 8, 1963 INVENTOR Roy E. WHEELER, 3y 7-,. :r/

ATTORNEY.

United States Patent 3,183,132 ELECTRIC SWITCH WITH CONTACT WELD CHECK MEANS Roy E. Wheeler, Champaign, Ill., assignor to General Electric Company, a corporation of New York Filed Apr. 8, 1963, Ser. No. 271,294 Claims. (Cl. 209-122) This invention relates to electric switches and has particular relation to electric overload actuated switches.

Overload actuated switches are widely employed in association with electrical apparatus to altord protection to such apparatus against current overload conditions. For example, an overload actuated switch may be utilized in association with an electric motor to effect deenergization of the motor in response to an overload condition of the motor current. Such a switch conventionally includes a bimetallic element which is heated and deflected in dependence upon the magnitude of motor current to actuate a movable contact out of engagement with a fixed contact in response to a current overload condition. Opening of the switch contacts is ordinarily employed to effect deenergization of a motor contactor for deenergizing the motor.

During usage of electric switches it is possible for the switch contacts to become welded together so that the movable contact cannot be moved out of engagement with the fixed contact in response to operation of the switch. If such contact welding occurs in an overload actuated switch it can result in damage to the protected apparatus due to failure of the contacts to open when a current overload condition exists.

In the design of overload actuated switches it is therefore very desirable that provision be made to permit rapid and convenient checking of the contacts to determine if they are welded together and to effectively break welds formed between the contacts. The contact weld cheek means should desirably be of inexpensive and compact construction so as not to add appreciably to the cost and overall dimensions of the switch. To provide a contact weld check in the past it has been necessary to disassemble the switch housing for permitting visual inspection of the contacts and then to break an existing weld by cumbersome manipulation of a suitable tool applied to the weld area which in many cases is inaccessible. It is thus desirable to provide contact weld check means which is conveniently operated without disassembling the switch housing by a simple operation performed externally of the housing.

It is accordingly an important object of the present invention to provide an electric switch having novel and improved means for effectively breaking a weld between the switch contacts.

It is another object of the invention to provide an electric switch having novel and improved means for breaking a weld between the switch contacts without disassembling the switch housing.

It is a further object of the invention to provide an electric switch having novel and improved manually actuatable means having an actuatable part outside the switch housing for applying a force to the movable switch contact which tends to break a weld between the switch contacts.

It is still another object of the invention to provide an electric switch having inexpensive and compact contact weld check means which is conveniently actuatable to break a weld between the switch contacts and which indicates the presence of a weld which is too strong to be broken by actuation of the means.

It is a still further object of the invention to provide a novel and improved overload actuated switch including fixed and movable contacts with overload responsive means for disengaging the contacts and a manually actuata-ble member which when actauted in one direction effects resetting of the contacts into engagement and when actuated in the opposite direction applies a force to the movable contact which tends to break a Weld between the contacts.

in carrying out the invention in one form an overload actuated switch is provided for protecting apparatus against overcurrent conditions. The switch includes an insulating housing which contains the operating parts including a fixed contact and a snap spring movable contact which normally engages the fixed contact to establish a control circuit and which is moved out of engagement therewith with a snap action to interrupt the control circu-it in response to deflection of a bimetallic element resulting from an overcurrent condition. The switch includes a manually actuatable bar which has an actuatabie portion outside the housing and which is guided by the housing for limited movement in opposing directions from a preselected position relative to the fixed and movable contacts. The bar includes within the housing a pair of longitudinally spaced projections which extend on opposite sides of the movable contact. When the bar is depressed into the housing from its preselected position, one of the projections effects resetting of the movable contact into snap engagement with the fixed contact when the contacts are disengaged, and when the bar is pulled outwardly of the housing from its preselected position the other projection applies a force to the movable contact tending to separate the contacts and break a weld formed between the contacts. Movement of the bar outwardly of the housing is limited so that the movable contact is moved away from the fixed contact without opening to its full extent with a snap action.

Other objects and advantages of the invention will become apparent from the following description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a view in elevation of an electric switch constructed according to the invention showing the actuatable bar in a manual reset position;

FIG. 2 is a fragmentary view in elevation of the switch of FIG. 1 showing the reset bar in an automatic reset position;

FIG. 3 is a view in elevation of the switch of FIGS. 1 and 2 with a part of the housing removed to expose the operating parts of the switch;

FIG. 4 is a view in section taken along the line 4-4 of FIG. 1 showing the relative positions of the reset bar and the switch contacts when the reset bar is in the manual position; and

FIG. 5 is a view in section taken along the line 55 of FIG. 3 showing in particular the movable contact.

Referring now to the drawings there is illustrated in FIG. 1 an electric switch constructed according to the invention and including an insulating housing 10 consisting of two separable parts 11 and 12, the part 12 supporting the operating parts of the switch as shown in FIGS. 3 and 4. Generally, these operating parts include a movable contact tip carrier 13 mounted for movement with respect to a fixed contact tip carrier 14, the contact tips normally being engaged and the carrier 13 being moved away from the contact carrier 14 in response to displacement of a plunger 15 (FIGS. 3 and 4) toward the right as viewed in FIG. 3 resulting from predetermined deflection of a main bimetal 16 which engages the left hand end of the plunger 15. A pair of compensating bimetals 17 and 18 (FIG. 3) engage the right hand end of plunger 15 to compensate for ambient temperature changes. A slidable bar 19 is mounted by the housing for the purpose of effecting either manual or automatic resetting of the movable contact tip into engagement with the fixed contact tip after the tips are disengaged.

More specifically, the switch includes a pair of spaced terminals 2% and 21 which are detachably mounted on the base of housing part 12 and which are adapted to be connected to an external circuit leading to the protected apparatus. The terminals 20 and 21 mount a resistance heating element 22 therebetween which is arranged to carry current in the external circuit and to heat the bimetallic element 16 which is thereby deflected by an amount dependent upon the magnitude of current in the external circuit. The bimetal 16 is supported in the housing part 12 at its ends to extend parallel to the heating element 22 with its high expansion side toward the right as viewed in FIG. 3 so as to bow toward the right to effect sliding movement of the plunger 15 toward the right against the bias exerted by the compensating bimetals 17 and 18. The plunger 15 is mounted for limited reciprocating movement within recesses formed in the housing part 12 and includes at its right hand end a restricted part 23 which extends through an opening of the compensating bimetal 17. The compensating bimetals are interconnected at their ends in bowed tensioned conditions to apply a force to plunger 15 in opposition to the force applied to the plunger by bimetal 16. The compensating bimetals have their high expansion portions at the outer sides thereof and heating of these bimetals by ambient temperature increases the force applied thereby to plunger 15 to provide ambient temperature compensation.

In order to effect movement of the movable contact carrier away from the fixed contact carrier in response to an overload condition of current in the external circuit, the plunger 15 is operatively connected to the contact carrier 13 and to this end includes a recess 24 in which is positioned a central tab 30 of the movable carrier 13 which is in the form of an electroconductive overcenter snap spring having spaced outer arms 31 on opposite sides of the tab 30 which straddle the plunger 15 and which are fixed to legs of an electroconductive support 32 located above the plunger as viewed in FIG. 3. Connected to and joining the legs 31 is a main contact tip carrying portion 33 which carries a contact tip 34 and which includes an extension 35 at its lower end which projects outwardly toward the right as viewed in FIG. 5. When tab 30 is to the left of center as shown in FIG. 3, the contact tip 34 is biased by its spring carrier into engagement with a fixed contact tip 36 on the carrier 14 which has a terminal part 37 outside the housing adapted for connection to a suitable control circuit (not shown) which may be provided to control energization of apparatus protected by the switch. The control circuit is also connected to an external part of an additional terminal 38 having inside the housing a part connected to the support 32 by means of an electroconductive strap 39. When the movable and fixed contact tips are disengaged, the control circuit connected to terminals 37 and'38 is interrupted.

In order to permit variation of the amount of current in the external circuit required to efifect separation of the contact tips, a calibrating screw 40 is rotatably mounted by the housing at its upper side to engage the upper section 41 of an L-shaped spring 42 having a vertically extending lower section 43 operatively connected to the plunger 15. The spring 42 is pivotally mounted by a portion 44 of the housing part 12 which engages the inside of the bend area of spring 42. When the screw 40 is rotated in a direction to depress the section 41 of spring 42, the plunger 15 is displaced toward the left against the bimetal 16 so that a greater amount of deflection of bimetal 16 and therefore a greater amount of current is required to separate the Contact tips. Rotation of screw 44 in the opposite direction will operate to move the plunger toward the right away from the bimetal 16 with the result that a lesser amount of current will be eifective to separate the contact tips.

When the bimetal 16 bows toward the right as viewed in FIG. 3 in response to current traversing the heating element 22, the plunger 15 is correspondingly displaced towards the right against the bias exerted by the compensating bimetals. When the plunger has been displaced to an extent such that the trailing wall of the recess 24 has carried the tab 30 of the contact carrier 13 to the right of center, the tip carrying portion of the carrier 13 is moved toward the left with a snap action to carry the movable contact tip out of engagement with the fixed contact tip. Resetting of the movable contact tip into engagement with the fixed contact tip may be done either manually or automatically as will be described more fully hereinafter.

In order to elfect resetting of the movable contact tip into engagement with the fixed contact tip the bar 19 is mounted by the housing for limited sliding movement relative to the fixed and movable contacts in opposing directions generally parallel to the direction of movement of the movable carrier 13. As shown in FIGS. 1 and 2, the bar 19 includes a manually actuatable handle part 45 outside the housing and is selectively positionable in either of two axial positions by means of a spring arm 46 mounted by the housing part 11 externally thereof and extending generally downwardly along a channel 47 formed in the outer surface of the housing part 11 and Opening at the lower edge thereof. One position of the bar 19, which will be termed a manual position, is shown in FIGS. 1, 3 and 4- and is established by positioning the spring arm an intermediate a pair of longitudinally spaced projections 48 and 41 on the outer surface of the bar 19 and extending into a slot 19 in the outer surface of the housing part 11. For this position of the bar 19 an elongated projection 51 extending downwardly from the lower surface of the bar as viewed in FIG. 4 is spaced from the movable carrier at the left thereof by an amount sufficient to permit full snap opening movement of the movable carrier in response to displacement of the plunger 15 toward the right. When the movable contact tip is out of engagement with the fixed tip, it is reset into engagement therewith by manual'depression of the bar 19 from its position shown in FIGS. 1, 3 and 4 inwardly of the housing against the bias of the spring arm 46 to an extent so that the projection St? is moved into engagement with the movable carrier to effect snap movement of the movable carrier towards the right which causes engagement of the movable and fixed contact tips. Inward movement of the bar 19 is limited by engagement of the right hand end of the bar 19 with a projection 51 of the housing. Release of the bar 19 from its depressed position results in return thereof to its manual posiltion under influence of the spring arm 46.

To provide for automatic resetting of the movable carrier the spring arm 46 is moved from its position shown in FIG. 1 to its position shown in FIG. 2 wherein the spring arm extends between the projection 49 and a projection 52 extending upwardly from the base of channel 47 to thereby reposition the bar 19 to the limit of its movement inwardly of the housing. For this automatic position of the bar 19, the bar 19 is restrained against longitudinal movement and the movable carrier is pre vented from snap opening to its full extent by means of the projection 511 which limits the opening movement of the movable carrier to a small amount. carrier is thus automatically returned into engagement with the fixed carrier in response to return movement of the plunger 15 toward the left as a result of the bias exerted thereon by the compensating thermostats as the main bimetal 16 cools.

In accordance with the present invention the switch is provided with novel and improved means for breaking a weld which may form between the movable and fixed contact tips. The weld check means is conveniently manually actuated from a position outside the housing to apply a force to the movable contact carrier 13 tending to move it away from the fixed contact carrier 14 to a limited extent. In the illustrated embodiment the The movable weld check means includes a part associated with the bar 19 in the form of a projection 55 of the bar 19 extending parallel to the projection 50 and defining therewith a plane which is generally parallel to the direction of movement of the movable carrier. As best shown in FIG. 4 the projection 55 is located at the right hand end of the bar 19 and is adapted to engage the carrier 13 as will presently appear.

When the bar 19 is positioned in its manual position, the

projections

50 and 55 extend downwardly as viewed in FIG. 4 on opposite sides of the movable carrier 13 with the projection 55 being closer to the movable carrier than the projection 56 and being aligned with the extension 35 of such carrier as viewed in FIG. 5. In order to perform a weld check the bar 19 is pulled outwardly of the housing from its manual position with the result that projection 55 is moved toward the left as viewed in FIG. 4 into engagement with the extension 35 of the movable carrier and deflects the end of the movable contact away from the fixed carrier in response to continued movement of the bar L7 in such direction. Movement of the bar 19 outwardly of the housing from its manual position is limited by engagement of the projection 48 with the left hand wall of the slot 49' formed in the housing member 11. The carrier 14 and the terminal 38 include recesses which allow passage of the

projections

50 and 55 past these parts in response to movement of the bar 19 outwardly of the housing. With the described arrangement the movable carrier is prevented from snap opening to its full extent in response to such movement of the bar 1) but is allowed to move a distance sufiicient to break a weld which may have formed between the tips 34 and '36. The positions of the projection 55' and the carrier 13 after full withdrawal of the bar 19 is shown in dash lines in FIG. 4. Release of the member 19 when in its fully withdrawn position permits the movable carrier 13 to return the bar 19 to its manual position by engagement of the carrier 13 and the projection 55 as the movable carrier springs back towards the fixed carrier.

If the contact tips are welded together, the above described movement of the bar 19 tends to break the weld and in most cases will actually do so. However, if the weld is too strong to be broken by the above described movement of the bar 19, this condition is indicated by failure of the control circuit to be interrupted. Such condition is also indicated by inability of the operator to withdraw the bar 19 outwardly of the housing from its manuaP position. In this event it is necessary to disassemble the housing and to physically separate the welded contact tips. It is thus seen that a very convenient and effective means is provided for breaking a weld b tween the fixed and movable contact tips, such means including a part of the usually present reset mechanism and being actuatable from a position outside the housing without requiring disassembly of the housing to break the weld except in extreme situations. If the bar 19 is in its automatic position and it is desired to make a weld check, it is only necessary to reposition the spring arm 46 and set the bar 19 in its manual position, and to eflfect movement of the bar 19 outwardly of the housing to the extent permitted.

While I have shown and described particular embodiments of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from my invention in its broader aspects and I, therefore, intend in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electric switch comprising, a fixed contact, a snap spring movable contact movable into and out of engagement with said fixed contact with a snap action, condition responsive means for effecting automatic movement of said movable contact out of engagement with said fixed contact, a manually actuatable member supported for movement relative to said contacts in opposing directions for resetting said contacts into engagement and for providing a contact weld check, means positioning said member in a predetermined normal axial position, said actuatable member being effective when actuated from said normal position in a first direction for moving said movable contact into engagement with said fixed contact to reset said contacts when the contacts are disengaged, and being effective when actuated from said normal position in a second direction opposite to the first direction for engaging and applying a force to the movable contact acting to move the movable contact out of engagement with the fixed contact when the contacts are engaged to provide a contact weld check, and means limiting movement of said member in said second direction to an extent permitting separation of said contacts without causing snap action of the movable contact.

2. An electric switch comprising, a fixed contact, a snap spring movable contact movable into and out of engagement with said fixed contact with a snap action, condition responsive means for efi'ecting automatic movement of said movable contact out of engagement with said fixed contact, a manually actuatable member supported for movement relative to said contacts in opposing directions for resetting said contacts into engagement and for providing a contact weld check, said actuatable member comprising an elongated bar having a pair of longitudinally spaced projections, means positioning said member in a predetermined normal axial position wherein said projections are longitudinally spaced from said movable contact on opposite sides thereof when said contacts are engaged, said bar when moved in a first direction from said normal position causing one of said projections to reset said movable contact into engagement with said fixed contact when the contacts are disengaged, said bar when moved in a second direction from said normal position opposite to said first direction causing the other projection to engage and apply a force to the movable contact acting to move the movable contact out of engagement with the fixed contact when the contacts are engaged to provide a contact weld check, and means limiting movement of said bar in said second direction to an extent permitting separation of said contacts by said other projection without causing snap action of the movable contact.

3. An electric switch comprising, a fixed contact, a snap spring movable contact movable into and out of engagement with said fixed contact with a snap action, condition responsive means for efiecting automatic movement of the movable contact out of engagement with the fixed contact, an elongated bar supported for movement along its axis relative to said contacts in opposing directions generally parallel to the direction of movement of said movable contact, said bar having a pair of longitudinally spaced projections extending on opposite sides of said movable contact, and resilient means for positioning said bar in a predetermined normal axial position wherein said projections are longitudinally spaced from said movable contact when said contacts are engaged and for resisting movement of said bar in a predetermined direction, said bar when moved from said normal position in a direction opposite to said predetermined direcion causing one of said projections to engage and apply a force to the movable contact acting to move the movable y contact out of engagement with the fixed contact when the contacts are engaged to provide a contact weld check, said bar when moved from said normal position in said predetermined direction causing the other projection to reset said movable contact into engagement with said fixed contact when said contacts are disengaged, and means limiting movement of said bar in said opposite direction to an extent permitting separation of said contacts by said one projection without causing snap action of the movable contact.

4. An electric switch comprising, a housing, a fixed contact in the housing, a snap spring movable contact in the housing movable into and out of engagement with said fixed contact with a snap action, means in the housing including a bimetallic strip for effecting movement of said movable contact out of engagement with the fixed contact, a manually actuatable elongated bar mounted by the housing for sliding movement along its axis relative to said contacts in directions inwardly and outwardly of the housing and generally parallel to the direction of movement of said movable contact, said bar having an actuatable portion outside the housing and having a pair of longitudinally spaced projections in the housing, said projections extending generally parallel to each other on opposite sides of said movable contact, resilient means for positioning said bar in a predetermined normal axial position wherein said projections are longitudinally spaced from said movable contact when said contacts are engaged, and for resisting movement of said bar in a direction inwardly of said housing, said bar when moved outwardly of said housing from said normal position causing one of said projections to engage and apply a force to the movable contact acting to move the movable contact out of engagement with the fixed contact when the contacts are engaged to provide a contact weld check, said bar when moved inwardly of said housing from said normal position causing the other projection to reset said movable contact into engagement with said fixed contact when said contacts are disengaged, and means limiting movement of said bar outwardly of said housing to an extent permitting separation of said contacts by said one projection without causing snap action of the movable contact.

5. An electric switch comprising, a housing, a fixed contact in the housing, a snap spring movable contact in the housing movable into and out of engagement with said fixed contact with a snap action, means in the housing including thermally responsive means for eifecting movement of said movable contact out of engagement with the fixed contact, a manually actuatable elongated bar mounted by the housing for sliding movement along its axis relative to said contacts in directions inwardly and outwardly of the housing and generally parallel to the direction of movement or" said movable contact, said bar having an actuatable portion outside the housing and having a pair of longitudinally spaced projections in the housing, said projections extending generally parallel to each other on opposite sides of said movable contact, resilient means supported by said housing and selectively positionable in either of two different positions relative to said bar, said resilient means when in one of said positions locating said bar in a first axial position wherein said projections are longitudinally spaced from said movable contact when said contacts are engaged, said bar when moved outwardly of said housing from said first position causing one of said projections to engage and apply a force to the movable contact acting to move the movable contact out of engagement with the fixed contact when the contacts are engaged to provide a contact weld check, said bar when in said first position locating the other projection so that it allows full snap movement of the movable contact away from the fixed contact, said bar when moved inwardly of said housing from said first position causing said other projection to reset said movable contact into engagement with said fixed contact when said contacts are disengaged, said resilient means when in the other of its positions locating said bar in a second axial position spaced inwardly of the housing relative to said first axial position of the bar, said bar when in said second axial position locating said other projection so that it engages and prevents full snap movement of the movable contact away from the fixed contact, and means limiting movement oi": said bar outwardly of the housing from the first axial position of the bar to anextent permitting separation of said contacts by said one projection without causing full snap movement of the movable contact away from the fixed contact.

References Cited by the Examiner UNITED STATES PATENTS 2,548,825 4/51 Schwend et al 2001 16 2,779,835 1/57 Russell 20076 2,863,022 12/58 Powell 200116 3,009,999 11/61 Johnson 200-1 16 3,015,007 12/61 Howard 200-114 3,03 8,051 6/62 Howard 74-342 BERNARD A. GILHEANY, Primary Examiner.

Claims

1. AN ELECTRIC SWITCH COMPRISING, A FIXED CONTACT, A SNAP SPRING MOVABLE CONTACT MOVABLE INTO AND OUT OF ENGAGEMENT WITH SAID FIXED CONTACT WITH A SNAP ACTION, CONDITION RESPONSIVE MEANS FOR EFFECTING AUTOMATIC MOVEMENT OF SAID MOVABLE CONTACT OUT OF ENGAGEMENT WITH SAID FIXED CONTACT, A MANUALLY ACTUATABLE MEMBER SUPPORTED FOR MOVEMENT RELATIVE TO SAID CONTACTS IN OPPOSING DIRECTIONS FOR RESETTING SAID CONTACTS INTO ENGAGEMENT AND FOR PROVIDING A CONTACT WELD CHECK, MEANS POSITIONING SAID MEMBER IN A PREDETERMINED NORMAL AXIAL POSITION, SAID ACTUABLE MEMBER BEING EFFECTIVE WHEN ACTUATED FROM SAID NORMAL POSITION IN A FIRST DIRECTION FOR MOVING SAID MOVABLE CONTACT INTO ENGAGEMENT WITH SAID FIXED CONTACT TO RESET SAID CONTACTS WHEN THE CONTACTS ARE DISENGAGED, AND BEING EFFECTIVE WHEN ACTUATED FROM SAID NORMAL POSITION IN A SECOND DIRECTION OPPOSITE TO THE FIRST DIRECTION FOR ENGAGING AND APPLYING A FORCE TO THE MOVABLE CONTACT ACT-